Add support for disabling pointer gestures.

Made it possible for individual windows to disable pointer gestures
while the window has focus using a private API.

Cleaned up the InputReader configuration code to enable in-place
reconfiguration of input devices without having to reopen them all.
This change makes changing the pointer speed somewhat nicer since the
pointer doesn't jump back to the origin after each change.

Change-Id: I9727419c2f4cb39e16acb4b15fd7fd84526b1239