Added shell command for some general input events

Added shell command for events DOWN, UP, and MOVE. This can be invoked
by calling 'adb shell input event <DOWN|UP|MOVE> <x> <y>'

This was needed to test transferTouchFocus, but can be useful for other
testing as well.

Test: 'adb shell input event <DOWN|UP|MOVE> <x> <y>'
Change-Id: If3e77b04c7172505e7fe8998b5b3c496044870bb