feat(SmallVideo.js): New interface.config property for dominant speaker icon disable

interface_config.js

     // Enables feedback star animation.
     ENABLE_FEEDBACK_ANIMATION: false,
     DISABLE_FOCUS_INDICATOR: false,
+    DISABLE_DOMINANT_SPEAKER_INDICATOR: false,
     AUDIO_LEVEL_PRIMARY_COLOR: "rgba(255,255,255,0.7)",
     AUDIO_LEVEL_SECONDARY_COLOR: "rgba(255,255,255,0.4)"
 };

modules/UI/videolayout/SmallVideo.js

  * @param show whether to show or hide.
  */
 SmallVideo.prototype.showDominantSpeakerIndicator = function (show) {
+    // Don't create and show dominant speaker indicator if
+    // DISABLE_DOMINANT_SPEAKER_INDICATOR is true
+    if (interfaceConfig.DISABLE_DOMINANT_SPEAKER_INDICATOR)
+        return;
+
     if (!this.container) {
         console.warn( "Unable to set dominant speaker indicator - "
             + this.videoSpanId + " does not exist");