Keyboard light: Fix the physical keyboard not light when it's visiable.

Change-Id: I595afd3cb6b422a17ae0f6ec20aa51979db13810
keyboard: adding functional alt/shift lights

This is useful for devices that has QWERTY keyboard
and leds for the Alt/Shift (Fn/Caps) keys, like
htc doubleshot.

Depends on libhardware patch for the light ids:
http://review.cyanogenmod.org/34902

Change-Id: I66ebc2d881438f5b51db77eaa885421e65a7da0d
Keep keyboard lit until the screen is dimmed

Do not use button timeout for keyboard (which is intrusive on QWERTY
sliders). Keep it lit until the screen dims instead of turning it off
like the buttons after 5 seconds. Also consider setting keyboard
visibility as a user activity.