Initial checkin of spot presentation for touchpad gestures.

Added a new PointerIcon API (hidden for now) for loading
pointer icons.

Fixed a starvation problem in the native Looper's sendMessage
implementation which caused new messages to be posted ahead
of old messages sent with sendMessageDelayed.

Redesigned the touch pad gestures to be defined in terms of
more fluid finger / spot movements.  The objective is to reinforce
the natural mapping between fingers and spots which means there
must not be any discontinuities in spot motion relative to
the fingers.

Removed the SpotController stub and folded its responsibilities
into PointerController.

Change-Id: I5126b1e69d95252fda7f2a684c9287e239a57163