Platform gesture

Provide gestures interfaces for both iOS and android.

Gesture recognition is implemented explicitly on individual platform, handled in the core by normalizing the gesture inputs from both the platforms.

This implementation provides naive handling from default gestures.

Some of the main TODOs include: 
a. Handling of continuous zoom
b. Account for zoom levels when panning.
Documentation says to use this if your application uses API 1.6 and above. However that being said, if we do not use "Compat" library it still works good. So should be good now.