[CORE] Move core plugins to a new modules directory

For reference (raised by rozzin in IRC):

* http://foldoc.org/module
* http://foldoc.org/library
* http://foldoc.org/plugin

As noted by XRevan86, modules are not necessarily non-essential.
As we will keep the modules directory in GS root [therefore, near to
plugins/], it is evidenced the difference between both.

This is a simple yet fundamental structural change. It doesn't change
functionality but makes clearer the way we understand GNU social's
internals.

lib/default.php

@@ -110,7 +110,7 @@ $default =
                 'softlimit' => '90%', // total size or % of memory_limit at which to restart queue threads gracefully
                 'spawndelay' => 1, // Wait at least N seconds between (re)spawns of child processes to avoid slamming the queue server with subscription startup
                 'debug_memory' => false, // true to spit memory usage to log
-              'breakout' => array(), // List queue specifiers to break out when using Stomp queue.
+                'breakout' => [], // List queue specifiers to break out when using Stomp queue.
                 // Default will share all queues for all sites within each group.
                 // Specify as <group>/<queue> or <group>/<queue>/<site>,
                 // using nickname identifier as site.
@@ -131,10 +131,10 @@ $default =
                 'params' => null,
                 'domain_check' => true),
         'nickname' =>
-        array('blacklist' => array(),
-              'featured' => array()),
+            array('blacklist' => [],
+                'featured' => []),
         'profile' =>
-        array('banned' => array(),
+            array('banned' => [],
                 'biolimit' => null,
                 'changenick' => false,
                 'allowprivate' => false,  // whether to allow setting stream to private ("only followers can read")
@@ -156,8 +156,8 @@ $default =
             ),
         'public' =>
             array('localonly' => false,
-              'blacklist' => array(),
-              'autosource' => array()),
+                'blacklist' => [],
+                'autosource' => []),
         'theme' =>
             array('server' => null,
                 'dir' => null,
@@ -210,7 +210,7 @@ $default =
         'cache' =>
             array('base' => null),
         'ping' =>
-        array('notify' => array(),
+            array('notify' => [],
                 'timeout' => 2),
         'inboxes' =>
             array('enabled' => true), # ignored after 0.9.x
@@ -326,46 +326,46 @@ $default =
                 'sharedefault' => false),
         'logincommand' =>
             array('disabled' => true),
-        'plugins' =>
-        array('core' => array(
-                            'ActivityVerb' => array(),
-                            'ActivityVerbPost' => array(),
-                            'ActivityModeration' => array(),
-                            'AuthCrypt' => array(),
-                            'Cronish' => array(),
-                            'Favorite' => array(),
-                            'HTMLPurifierSchemes' => array(),
-                            'Share' => array(),
-                            'LRDD' => array(),
-                        ),
-              'default' => array(
-                            'Activity' => array(),
-                            'AntiBrute' => array(),
-                            'Blacklist' => array(),
-                            'Bookmark' => array(),
-                            'ClientSideShorten' => array(),
-                            'DefaultLayout' => array(),
-                            'Directory' => array(),
-                            'DirectMessage' => array(),
-                            'EmailAuthentication' => array(),
-                            'Event' => array(),
-                            'Embed' => array(),
-                            'OpenID' => array(),
-                            'OpportunisticQM' => array(),
-                            'ActivityPub' => array(),
-                            'OStatus' => array(),
-                            'Poll' => array(),
-                            'SimpleCaptcha' => array(),
-                            'TagSub' => array(),
-                            'WebFinger' => array(),
-                            'Nodeinfo' => array(),
-                        ),
+        'plugins' =>[
+            'core' => [
+                'Activity' => [],
+                'ActivityModeration' => [],
+                'ActivityVerb' => [],
+                'ActivityVerbPost' => [],
+                'AuthCrypt' => [],
+                'Favorite' => [],
+                'HTMLPurifierSchemes' => [],
+                'Share' => [],
+            ],
+            'default' => [
+                'AntiBrute' => [],
+                'Blacklist' => [],
+                'Bookmark' => [],
+                'ClientSideShorten' => [],
+                'Cronish' => [],
+                'DefaultLayout' => [],
+                'DirectMessage' => [],
+                'Directory' => [],
+                'EmailAuthentication' => [],
+                'Embed' => [],
+                'Event' => [],
+                'LRDD' => [],
+                'Nodeinfo' => [],
+                'OpenID' => [],
+                'OpportunisticQM' => [],
+                'ActivityPub' => [], // The order is important here (IT HAS TO COME BEFORE OSTATUS)
+                'OStatus' => [],
+                'Poll' => [],
+                'SimpleCaptcha' => [],
+                'TagSub' => [],
+                'WebFinger' => [],
+            ],
             'locale_path' => false, // Set to a path to use *instead of* each plugin's own locale subdirectories
             'server' => null,
             'sslserver' => null,
             'path' => null,
             'sslpath' => null,
-              ),
+        ],
         'admin' =>
             array('panels' => array('site', 'user', 'paths', 'access', 'sessions', 'sitenotice', 'license', 'plugins')),
         'singleuser' =>

lib/event.php

@@ -82,7 +82,7 @@ class Event {
      *                 on results of handlers.
      */
 
-    public static function handle($name, array $args=array()) {
+    public static function handle($name, array $args = []) {
         $result = null;
         if (array_key_exists($name, Event::$_handlers)) {
             foreach (Event::$_handlers[$name] as $handler) {

lib/gnusocial.php

@@ -30,7 +30,7 @@ class GNUsocial
     protected static $plugins = array();
 
     /**
-     * Configure and instantiate a plugin into the current configuration.
+     * Configure and instantiate a plugin (or a core module) into the current configuration.
      * Class definitions will be loaded from standard paths if necessary.
      * Note that initialization events won't be fired until later.
      *
@@ -39,7 +39,7 @@ class GNUsocial
      *
      * @throws ServerException if plugin can't be found
      */
-    public static function addPlugin($name, array $attrs=array())
+    public static function addPlugin($name, array $attrs = [])
     {
         $name = ucfirst($name);
 
@@ -54,12 +54,16 @@ class GNUsocial
 
         if (!class_exists($pluginclass)) {
 
-            $files = array("local/plugins/{$pluginclass}.php",
+            $files = [
+                "local/plugins/{$pluginclass}.php",
                 "local/plugins/{$name}/{$pluginclass}.php",
                 "local/{$pluginclass}.php",
                 "local/{$name}/{$pluginclass}.php",
+                "modules/{$pluginclass}.php",
+                "modules/{$name}/{$pluginclass}.php",
                 "plugins/{$pluginclass}.php",
-                           "plugins/{$name}/{$pluginclass}.php");
+                "plugins/{$name}/{$pluginclass}.php"
+            ];
 
             foreach ($files as $file) {
                 $fullpath = INSTALLDIR.'/'.$file;

lib/plugin.php

@@ -64,9 +64,9 @@ class Plugin
     }
 
     /**
-     * Load related modules when needed
+     * Load related components when needed
      *
-     * Most non-trivial plugins will require extra modules to do their work. Typically
+     * Most non-trivial plugins will require extra components to do their work. Typically
      * these include data classes, action classes, widget classes, or external libraries.
      *
      * This method receives a class name and loads the PHP file related to that class. By
@@ -79,11 +79,14 @@ class Plugin
      *
      * @param string $cls Name of the class to be loaded
      *
-     * @return boolean hook value; true means continue processing, false means stop.
+     * @return bool hook value; true means continue processing, false means stop.
      */
     public function onAutoload($cls) {
         $cls = basename($cls);
         $basedir = INSTALLDIR . '/local/plugins/' . mb_substr(get_called_class(), 0, -6);
+        if (!file_exists($basedir)) {
+            $basedir = INSTALLDIR . '/modules/' . mb_substr(get_called_class(), 0, -6);
+        }
         if (!file_exists($basedir)) {
             $basedir = INSTALLDIR . '/plugins/' . mb_substr(get_called_class(), 0, -6);
         }
@@ -92,17 +95,17 @@ class Plugin
 
         if (preg_match('/^(\w+)(Action|Form)$/', $cls, $type)) {
             $type = array_map('strtolower', $type);
-            $file = "$basedir/{$type[2]}s/{$type[1]}.php";
+            $file = "{$basedir}/{$type[2]}s/{$type[1]}.php";
         }
         if (!file_exists($file)) {
-            $file = "$basedir/classes/{$cls}.php";
+            $file = "{$basedir}/classes/{$cls}.php";
 
             // library files can be put into subdirs ('_'->'/' conversion)
             // such as LRDDMethod_WebFinger -> lib/lrddmethod/webfinger.php
             if (!file_exists($file)) {
                 $type = strtolower($cls);
                 $type = str_replace('_', '/', $type);
-                $file = "$basedir/lib/{$type}.php";
+                $file = "{$basedir}/lib/{$type}.php";
             }
         }
 
@@ -127,9 +130,12 @@ class Plugin
             if (!$path) {
                 // @fixme this will fail for things installed in local/plugins
                 // ... but then so will web links so far.
-                $path = INSTALLDIR . "/plugins/$name/locale";
+                $path = INSTALLDIR . "/plugins/{$name}/locale";
                 if (!file_exists($path)) {
-                    $path = INSTALLDIR . "/local/plugins/$name/locale";
+                    $path = INSTALLDIR . "/modules/{$name}/locale";
+                }
+                if (!file_exists($path)) {
+                    $path = INSTALLDIR . "/local/plugins/{$name}/locale";
                 }
             }
             if (file_exists($path) && is_dir($path)) {
@@ -208,6 +214,8 @@ class Plugin
             // XXX: extra stat().
             if (@file_exists(PUBLICDIR . '/local/plugins/' . $plugin . '/' . $relative)) {
                 $path = common_config('site', 'path') . '/local/plugins/';
+            } elseif (@file_exists(PUBLICDIR . '/modules/' . $plugin . '/' . $relative)) {
+                $path = common_config('site', 'path') . '/modules/';
             } else {
                 $path = common_config('site', 'path') . '/plugins/';
             }