Implement TrackballControls.unlisten.

Without this method, TrackballControls will always be bound to window.keyDown or window.keyUp, and will never be garbage-collected (including references in closures called on change).
Fix: Use setFrom instead of assignment for Vector members.
Bring up to date compared to three.js, with respect to touch support.
Bring up to date compared to three.js, dispatch startEvent and endEvent.
Provide optional autoUpdate.
Merge pull request #159 from johsin18/fix-trackball-touch

Fix trackball in terms of touch support