Improve auto-brightness handling

- Add a setting to control the auto-brightness algorithm responsitivity
- Make the algorithm react much faster when the ambient brightness
  increases quickly, e.g. when receiving a call in bright sunlight.

Change-Id: I21645ed3eba2ad142136e0f3e3554210f0a2ab36
Signed-off-by: Dan Trifan <jimsth@gmail.com>
HALO: keep apps in recents

Change-Id: I0cc25df8685113f4c9903beee09c6001f959e574
Signed-off-by: Dan Trifan <jimsth@gmail.com>