feat(ParticipantConnectionStatus): add init and dispose methods

JitsiConference.js

 
     this.participantConnectionStatus
         = new ParticipantConnectionStatus(this.rtc, this);
+    this.participantConnectionStatus.init();
 
     if(!this.statistics) {
         this.statistics = new Statistics(this.xmpp, {
 JitsiConference.prototype.leave = function () {
     var conference = this;
 
+    if (this.participantConnectionStatus) {
+        this.participantConnectionStatus.dispose();
+        this.participantConnectionStatus = null;
+    }
+
     this.statistics.stopCallStats();
     this.rtc.closeAllDataChannels();
 

modules/connectivity/ParticipantConnectionStatus.js

 function ParticipantConnectionStatus(rtc, conference) {
     this.rtc = rtc;
     this.conference = conference;
-    rtc.addListener(
-        RTCEvents.ENDPOINT_CONN_STATUS_CHANGED,
-        this.onEndpointConnStatusChanged.bind(this));
 }
 
+/**
+ * Initializes <tt>ParticipantConnectionStatus</tt> and bind required event
+ * listeners.
+ */
+ParticipantConnectionStatus.prototype.init = function() {
+
+    this._onEndpointConnStatusChanged
+        = this.onEndpointConnStatusChanged.bind(this);
+
+    this.rtc.addListener(
+        RTCEvents.ENDPOINT_CONN_STATUS_CHANGED,
+        this._onEndpointConnStatusChanged);
+};
+
+/**
+ * Removes all event listeners and disposes of all resources held by this
+ * instance.
+ */
+ParticipantConnectionStatus.prototype.dispose = function () {
+
+    this.rtc.removeListener(
+        RTCEvents.ENDPOINT_CONN_STATUS_CHANGED,
+        this._onEndpointConnStatusChanged);
+};
+
 /**
  * Handles RTCEvents.ENDPOINT_CONN_STATUS_CHANGED triggered when we receive
  * notification over the data channel from the bridge about endpoint's