Support GESTURE_SENSOR input device type with GestureService

* The GESTURE_SENSOR input device type is meant to support touch sensors
  which are meant for gesture input only, very similar to a touchpad,
  but without the pointer capability.
* Define separate service to handle gestures from GESTURE_SENSOR device
  type.

Change-Id: I9b273df2a3cc141774d7f7cd81e43a90ea5b230b
Hide InputDevice.SOURCE_GESTURE_SENSOR from API

Change-Id: If009e9595fc593594b0e7764669996de137483a1