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
diff --git a/include/ui/Keyboard.h b/include/ui/Keyboard.h
index 50296e2..54bc968 100644
--- a/include/ui/Keyboard.h
+++ b/include/ui/Keyboard.h
@@ -111,6 +111,18 @@
 extern uint32_t getKeyFlagByLabel(const char* label);
 
 /**
+ * Gets a axis by its short form label, eg. "X".
+ * Returns -1 if unknown.
+ */
+extern int32_t getAxisByLabel(const char* label);
+
+/**
+ * Gets a axis label by its id.
+ * Returns NULL if unknown.
+ */
+extern const char* getAxisLabel(int32_t axisId);
+
+/**
  * Updates a meta state field when a key is pressed or released.
  */
 extern int32_t updateMetaState(int32_t keyCode, bool down, int32_t oldMetaState);