handle PRESENCE_STATUS event

JitsiConference.js

         conference.eventEmitter.emit(JitsiConferenceEvents.MESSAGE_RECEIVED, id, txt, ts);
     });
 
+    conference.room.addListener(XMPPEvents.PRESENCE_STATUS, function (jid, status) {
+        var id = Strophe.getResourceFromJid(jid);
+        var participant = conference.getParticipantById(id);
+        if (!participant || participant._status === status) {
+            return;
+        }
+        participant._status = status;
+        conference.eventEmitter.emit(JitsiConferenceEvents.USER_STATUS_CHANGED, id, status);
+    });
+
     conference.rtc.addListener(DSEvents.FIREFOX_EXTENSION_NEEDED, function (url) {
         conference.eventEmitter.emit(JitsiConferenceEvents.FIREFOX_EXTENSION_NEEDED, url);
     });

JitsiConferenceEvents.js

      * User role changed.
      */
     USER_ROLE_CHANGED: "conference.roleChanged",
+    /**
+     * User status changed.
+     */
+    USER_STATUS_CHANGED: "conference.statusChanged",
     /**
      * New text message was received.
      */

JitsiParticipant.js

     this._supportsDTMF = false;
     this._tracks = [];
     this._role = 'none';
+    this._status = null;
 }
 
 /**
     return this._displayName;
 };
 
+/**
+ * @returns {String} The status of the participant.
+ */
+JitsiParticipant.prototype.getStatus = function () {
+    return this._status;
+};
+
 /**
  * @returns {Boolean} Whether this participant is a moderator or not.
  */

doc/API.md

         - CONFERENCE_LEFT - notifies the local user that he left the conference successfully. (no parameters)
         - DTMF_SUPPORT_CHANGED - notifies if at least one user supports DTMF. (parameters - supports(boolean))
         - USER_ROLE_CHANGED - notifies that role of some user changed. (parameters - id(string), role(string))
+        - USER_STATUS_CHANGED - notifies that status of some user changed. (parameters - id(string), status(string))
         - CONFERENCE_FAILED - notifies that user failed to join the conference. (parameters - errorCode(JitsiMeetJS.errors.conference))
         - KICKED - notifies that user has been kicked from the conference.
         - START_MUTED_POLICY_CHANGED - notifies that all new participants will join with muted audio/video stream (parameters - JS object with 2 properties - audio(boolean), video(boolean))

modules/RTC/DataChannels.js

 }
 
 module.exports = DataChannels;
-

modules/xmpp/ChatRoom.js

 
     // Trigger status message update
     if (member.status) {
-        this.eventEmitter.emit(XMPPEvents.PRESENCE_STATUS, from, member);
+        this.eventEmitter.emit(XMPPEvents.PRESENCE_STATUS, from, member.status);
     }
 
     if(jibri)