cyapa - Adjust button and multi-touch handling a bit

cyapa - Adjust button and multi-touch handling a bit

* If you finger-move more than 16 pixels, the button press will always
  be registered as a LEFT button press.

  This makes it much easier to move around the pad and hit GUI buttons, move
  windows around, etc.

* Three fingers simulates the left button without actually having to hit it.
  (it's too easy to accidently have two fingers down so we don't simulate
  the left button with two fingers).  This makes it even easier to move
  windows around and hit GUI buttons.

* If you just hit the button without a finger-move, the button press will
  be LEFT, MIDDLE, or RIGHT depending on where you are on the pad, as before.

* Track identifiers when multiple fingers are down.  The trackpad can track
  up to 5 fingers.  Use the identifier tracking to avoid jumping the
  coordinates to a different finger (which would cause the mouse to jump).

  This results in much easier mouse movement.