add pinch, spread, rotate and inward/outward pan gestures

Now there are 15 detectable gestures, namely:
	* tap
	* pan
	* hold
	* swipe
	* pinch
	* spread
	* rotate
	* double_tap
	* inward_pan
	* outward_pan
	* pan_release
	* two_finger_tap
	* two_finger_pan
	* two_finger_swipe
	* two_finger_pan_release