Approve room invitations

We use to rely on Empathy for this but as we plan to allow users to be
connected on IM without having Empathy running the Shell should do it now.

https://bugzilla.gnome.org/show_bug.cgi?id=653740

js/ui/notificationDaemon.js

@@ -190,9 +190,10 @@ NotificationDaemon.prototype = {
                      actions, hints, timeout) {
         let id;
 
-        // Filter out chat and presence notifications from Empathy, since we
+        // Filter out chat, presence and invitation notifications from Empathy, since we
         // handle that information from telepathyClient.js
         if (appName == 'Empathy' && (hints['category'] == 'im.received' ||
+              hints['category'] == 'x-empathy.im.room-invitation' ||
               hints['category'] == 'presence.online' ||
               hints['category'] == 'presence.offline')) {
             // Ignore replacesId since we already sent back a