Handles graceful-shutdown focus error response.

index.html

     <script src="libs/popover.js?v=1"></script><!-- bootstrap tooltip lib -->
     <script src="libs/toastr.js?v=1"></script><!-- notifications lib -->
     <script src="interface_config.js?v=5"></script>
-    <script src="libs/app.bundle.js?v=21"></script>
+    <script src="libs/app.bundle.js?v=22"></script>
     <script src="analytics.js?v=1"></script><!-- google analytics plugin -->
     <link rel="stylesheet" href="css/font.css?v=6"/>
     <link rel="stylesheet" href="css/toastr.css?v=1">

lang/main.json

         "settings2": "Participants join muted",
         "settings3": "Require nicknames<br/><br/>Set a password to lock your room:",
         "yourPassword": "your password",
-        "Back": "Back"
+        "Back": "Back",
+        "serviceUnavailable": "Service unavailable",
+        "gracefulShutdown": "Our service is currently down for maintenance. Please try again later."
     }
 }

modules/UI/UI.js

     APP.connectionquality.addListener(CQEvents.STOP,
         VideoLayout.onStatsStop);
     APP.xmpp.addListener(XMPPEvents.DISPOSE_CONFERENCE, onDisposeConference);
+    APP.xmpp.addListener(XMPPEvents.GRACEFUL_SHUTDOWN, function () {
+        messageHandler.openMessageDialog(
+            'dialog.serviceUnavailable', 'Service unavailable',
+            'dialog.gracefulShutdown',
+            'Our service is currently down for maintenance.' +
+            ' Please try again later.'
+        );
+    });
     APP.xmpp.addListener(XMPPEvents.KICKED, function () {
         messageHandler.openMessageDialog("dialog.sessTerminated", "Session Terminated",
             "dialog.kickMessage", "Ouch! You have been kicked out of the meet!");

modules/xmpp/moderator.js

                     console.info("Session expired! - removing");
                     localStorage.removeItem("sessionId");
                 }
+                if ($(error).find('>error>graceful-shutdown').length) {
+                    eventEmitter.emit(XMPPEvents.GRACEFUL_SHUTDOWN);
+                    return;
+                }
                 // Not authorized to create new room
                 if ($(error).find('>error>not-authorized').length) {
                     console.warn("Unauthorized to start the conference", error);

service/xmpp/XMPPEvents.js

     CALL_TERMINATED: "xmpp.callterminated.jingle",
     CALL_INCOMING: "xmpp.callincoming.jingle",
     DISPOSE_CONFERENCE: "xmpp.dispoce_confernce",
+    GRACEFUL_SHUTDOWN: "xmpp.graceful_shutdown",
     KICKED: "xmpp.kicked",
     BRIDGE_DOWN: "xmpp.bridge_down",
     USER_ID_CHANGED: "xmpp.user_id_changed",