propagate FOCUS_LEFT conference error

JitsiConference.js

     conference.room.addListener(XMPPEvents.FOCUS_DISCONNECTED, function (focus, retrySec) {
         conference.eventEmitter.emit(JitsiConferenceEvents.CONFERENCE_FAILED, JitsiConferenceErrors.FOCUS_DISCONNECTED, focus, retrySec);
     });
+    conference.room.addListener(XMPPEvents.FOCUS_LEFT, function () {
+        conference.eventEmitter.emit(JitsiConferenceEvents.CONFERENCE_FAILED, JitsiConferenceErrors.FOCUS_LEFT);
+    });
 //    FIXME
 //    conference.room.addListener(XMPPEvents.MUC_JOINED, function () {
 //        conference.eventEmitter.emit(JitsiConferenceEvents.CONFERENCE_LEFT);
             conference.eventEmitter.emit(JitsiConferenceEvents.LAST_N_ENDPOINTS_CHANGED,
                 lastNEndpoints, endpointsEnteringLastN);
         });
-    conference.xmpp.addListener(XMPPEvents.PASSWORD_REQUIRED, function () {
-        conference.eventEmitter.emit(JitsiConferenceErrors.PASSWORD_REQUIRED);
-    });
 
     conference.xmpp.addListener(XMPPEvents.START_MUTED_FROM_FOCUS,
         function (audioMuted, videoMuted) {

JitsiConferenceErrors.js

     /**
      * Indicates that focus error happened.
      */
-    FOCUS_DISCONNECTED: "conference.focusDisconnected"
+    FOCUS_DISCONNECTED: "conference.focusDisconnected",
+    /**
+     * Indicates that focus left the conference.
+     */
+    FOCUS_LEFT: "conference.focusLeft"
     /**
      * Many more errors TBD here.
      */

doc/API.md

         - CONFERENCE_DESTROYED - conference has been destroyed
         - CHAT_ERROR - chat error happened
         - FOCUS_DISCONNECTED - focus error happened
+        - FOCUS_DISCONNECTED - focus left the conference
     2. connection
         - PASSWORD_REQUIRED - passed when the connection to the server failed. You should try to authenticate with password.
         - CONNECTION_ERROR - indicates connection failures.

modules/xmpp/moderator.js

     if (resource === 'focus' && !this.xmppService.sessionTerminated) {
         logger.info(
             "Focus has left the room - leaving conference");
-        //hangUp();
-        // We'd rather reload to have everything re-initialized
-        //FIXME: show some message before reload
         this.eventEmitter.emit(XMPPEvents.FOCUS_LEFT);
     }
 };