policy: Long-press power while display is off for torch

Long-press the power button while the display is off
to turn the torchlight on and off.

Credits:
 - Lion0738: The main hooks here:
   https://github.com/lion0738/android_frameworks_base/commit/9af2b7844a4d973c8b6c542d7937f56a24a7e5f1
 - Atlantis: The logic on where to hook into this for power button only
 - Alex Cruz: Helping and giving me some pointers along the way

Change-Id: I14365389990eb06daaa127f5db66df45abf6c064
(cherry picked from commit 604f00ce)