Fixes issues related to PR #451

JitsiConference.js

 var XMPPEvents = require("./service/xmpp/XMPPEvents");
 var AuthenticationEvents = require("./service/authentication/AuthenticationEvents");
 var RTCEvents = require("./service/RTC/RTCEvents");
-var DSEvents = require("./service/desktopsharing/DesktopSharingEventTypes");
 var EventEmitter = require("events");
 var JitsiConferenceEvents = require("./JitsiConferenceEvents");
 var JitsiConferenceErrors = require("./JitsiConferenceErrors");
         conference.eventEmitter.emit(JitsiConferenceEvents.CONFERENCE_FAILED, JitsiConferenceErrors.CONFERENCE_DESTROYED, reason);
     });
     conference.room.addListener(XMPPEvents.CHAT_ERROR_RECEIVED, function (err, msg) {
-        conference.eventEmitter.emit(JitsiConferenceEvents.CONFERENCE_FAILED, JitsiConferenceErrors.CHAT_ERROR, err, msg);
+        conference.eventEmitter.emit(JitsiConferenceEvents.CONFERENCE_ERROR, JitsiConferenceErrors.CHAT_ERROR, err, msg);
     });
     conference.room.addListener(XMPPEvents.FOCUS_DISCONNECTED, function (focus, retrySec) {
         conference.eventEmitter.emit(JitsiConferenceEvents.CONFERENCE_FAILED, JitsiConferenceErrors.FOCUS_DISCONNECTED, focus, retrySec);
         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);
-    });
-
     conference.rtc.addListener(RTCEvents.DOMINANTSPEAKER_CHANGED, function (id) {
         if(conference.lastDominantSpeaker !== id && conference.room) {
             conference.lastDominantSpeaker = id;

JitsiConferenceErrors.js

      */
     CONFERENCE_DESTROYED: "conference.destroyed",
     /**
-     * Indicates that chat error occured.
+     * Indicates that chat error occurred.
      */
     CHAT_ERROR: "conference.chatError",
     /**

JitsiConferenceEvents.js

      * Indicates that conference failed.
      */
     CONFERENCE_FAILED: "conference.failed",
+    /**
+     * Indicates that an error occured.
+     */
+    CONFERENCE_ERROR: "conference.error",
     /**
      * Indicates that conference has been joined.
      */
      * Indicates that phone number changed.
      */
     PHONE_NUMBER_CHANGED: "conference.phoneNumberChanged",
-    /**
-     * Indicates that to proceed with screen sharing
-     * browser extension must be installed first.
-     */
-    FIREFOX_EXTENSION_NEEDED: "conference.firefoxExtensionRequired",
     /**
      * Indicates that available devices changed.
      */

doc/API.md

         - 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))
+        - CONFERENCE_ERROR - notifies that error occurred. (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))
         - STARTED_MUTED - notifies that the local user has started muted
-        - FIREFOX_EXTENSION_NEEDED - notifies that browser extension must be installed to proceed with screen sharing (parameters - extension url(string))
         - AVAILABLE_DEVICES_CHANGED - notifies that available participant devices changed (camera or microphone was added or removed) (parameters - id(string), devices(JS object with 2 properties - audio(boolean), video(boolean)))
 
     2. connection
 * ```JitsiMeetJS.errors``` - JS object that contains all errors used by the API. You can use that object to check the reported errors from the API
     We have two error types - connection and conference. You can access the events with the following code ```JitsiMeetJS.errors.<error_type>.<error_name>```.
     For example if you want to use the conference event that is fired when somebody leave conference you can use the following code - ```JitsiMeetJS.errors.conference.PASSWORD_REQUIRED```.
-    We support the following events:
+    We support the following errors:
     1. conference
         - CONNECTION_ERROR - the connection with the conference is lost.
         - SETUP_FAILED - conference setup failed