Added saveActivity method to Notice class

saveActivity will accept an Activity which gets parsed and saved through
plugins. So when an ActivityHandlerPlugin (such as Favorite will be soon)
gets a feed to save, this will be the function called instead of saveNew.

plugins/OStatus/OStatusPlugin.php

@@ -1360,4 +1360,9 @@ class OStatusPlugin extends Plugin
 
         return true;
     }
+
+    public function onGetLocalAttentions(Profile $actor, array $attention_uris, array &$mentions, array &$groups)
+    {
+        list($mentions, $groups) = Ostatus_profile::filterAttention($actor, $attention_uris);
+    }
 }