plugin XEP-0060: added an config option to set pubsub service

"pubsub_service" can now be used in [DEFAULT] section. If not found or invalid, first pubsub service found will be used

fix 216

src/plugins/plugin_xep_0060.py

@@ -121,7 +121,11 @@ class XEP_0060(object):
     @defer.inlineCallbacks
     def profileConnected(self, client):
         client.pubsub_watching = set()
-        client.pubsub_service = yield self.host.findServiceEntity(client, "pubsub", "service")
+        try:
+            client.pubsub_service = jid.JID(self.host.memory.getConfig('', 'pubsub_service'))
+        except RuntimeError:
+            log.info(_(u"Can't retrieve pubsub_service from conf, we'll use first one that we find"))
+            client.pubsub_service = yield self.host.findServiceEntity(client, "pubsub", "service")
 
     def getFeatures(self, profile):
         try: