Gesture binding on Media Player

-Added onGesture(gesture,callback) to the Media object in javascript so gestures can be bound during media playback.
-MediaPlayerFragment's onGesture(...) posts MediaGestureEvents to the EventBus.
-MediaManager handles callback registration during media playback.
-MediaManager subscribes to MediaGestureEvents and calls corresponding callback.
-MediaManager initialization in ManagerManager.
Stable FastForward and Rewind

-Added smoother reversePlayback and FastForward to media object.