Add new axes for joysticks and mouse wheels.

Added API on InputDevice to query the set of axes available.
Added API on KeyEvent and MotionEvent to convert keycodes and axes
to symbolic name strings for diagnostic purposes.
Added API on KeyEvent to query if a given key code is a gamepad button.
Added a new "axis" element to key layout files to specify the
mapping between raw absolute axis values and motion axis ids.
Expanded the axis bitfield to 64bits to allow for future growth.
Modified the Makefile for keyboard prebuilts to run the keymap
validation tool during the build.
Added layouts for two game controllers.
Added default actions for game pad button keys.
Added more tests.
Fixed a bunch of bugs.

Change-Id: I73f9166c3b3c5bcf4970845b58088ad467525525