Introduces new config ignoreStartMuted, ignores start muted option. (#428)

Ignores start audio/video muted requests received by jicofo.

JitsiConferenceEventManager.js

 
     conference.xmpp.addListener(XMPPEvents.START_MUTED_FROM_FOCUS,
         (audioMuted, videoMuted) => {
+            if (conference.options.config.ignoreStartMuted) {
+                return;
+            }
+
             conference.startAudioMuted = audioMuted;
             conference.startVideoMuted = videoMuted;
 

doc/API.md

         4. callStatsID - callstats credentials
         5. callStatsSecret - callstats credentials
         6. enableTalkWhileMuted - boolean property. Enables/disables talk while muted detection, by default the value is false/disabled.
+        7. ignoreStartMuted - ignores start muted events coming from jicofo. 
         **NOTE: if 4 and 5 are set the library is going to send events to callstats. Otherwise the callstats integration will be disabled.**
 
 5. addEventListener(event, listener) - Subscribes the passed listener to the event.