OStatus group delivery initial implementation.

- added rel="ostatus:attention" links for group delivery
- added events for plugins to override group profile/permalink pages
- pulled Notice::saveGroups up to save-time so we can override;
  it's relatively cheap and gives us a clean list of target
  groups for distrib time even with customized delivery.
- fixed notice::getGroups to return group objects as expected
- added some doc on new parameters to Notice::saveNew
 - 'groups' list of group IDs to push to in place of parsing
- messages that come in via PuSH and contain local group targets
  are delivered to local group members
- messages that come in via PuSH and contain remote group targets
  are delivered to local members of the remote group

Todo:
- handle group posts that only come through Salmon
- handle conflicts in case something comes in both through Salmon and PuSH
- better source verification
- need a cleaner interface to look up groups by URI
- need a way to handle remote groups with conflicting names

plugins/OStatus/OStatusPlugin.php

@@ -591,6 +591,22 @@ class OStatusPlugin extends Plugin
         return true;
     }
 
+    function onStartUserGroupHomeUrl($group, &$url)
+    {
+        return $this->onStartUserGroupPermalink($group, &$url);
+    }
+
+    function onStartUserGroupPermalink($group, &$url)
+    {
+        $oprofile = Ostatus_profile::staticGet('group_id', $group->id);
+        if ($oprofile) {
+            // @fixme this should probably be in the user_group table
+            // @fixme this uri not guaranteed to be a profile page
+            $url = $oprofile->uri;
+            return false;
+        }
+    }
+
     function onStartShowSubscriptionsContent($action)
     {
         $user = common_current_user();