First steps on converting FeedSub into the pub/sub basis for OStatus communications:

* renamed FeedSub plugin to OStatus
* now setting avatar on subscriptions
* general fixes for subscription
* integrated PuSH hub to handle only user timelines on canonical ID url; sends updates directly
* set $config['feedsub']['nohub'] = true to test w/ foreign feeds that don't have hubs (won't actually receive updates though)
* a few bits of code documentation
* HMAC support for verified distributions (safest if sub setup is on HTTPS)

And a couple core changes:
* minimizing HTML output for exceptions in API requests to aid in debugging
* fix for rel=self link in apitimelineuser when id given

This does not not yet include any of the individual subscription management (Salmon notifications for sub/unsub, etc) nor a nice UI for user subscriptions.
Needs some further cleanup to treat posts as status updates instead of link references.

lib/statusnet.php

@@ -30,6 +30,7 @@ global $config, $_server, $_path;
 class StatusNet
 {
     protected static $have_config;
+    protected static $is_api;
 
     /**
      * Configure and instantiate a plugin into the current configuration.
@@ -63,7 +64,7 @@ class StatusNet
                 }
             }
             if (!class_exists($pluginclass)) {
-                throw new ServerException(500, "Plugin $name not found.");
+                throw new ServerException("Plugin $name not found.", 500);
             }
         }
 
@@ -147,6 +148,16 @@ class StatusNet
         return self::$have_config;
     }
 
+    public function isApi()
+    {
+        return self::$is_api;
+    }
+    
+    public function setApi($mode)
+    {
+        self::$is_api = $mode;
+    }
+
     /**
      * Build default configuration array
      * @return array