ActiveScreen: added option for Pocket mode
This makes active screen proximity sensor based behavior optional.
The "Proximity wake-up" feature in Power tweaks has higher priority thus
overrides Pocket mode option in Active Screen settings.

Plus:
- active screen preference revamped
- optimized by utilizing new "notification extras emulation".

Conflicts:
	res/values-cs/strings.xml
	res/values-sk/strings.xml
	res/values/strings.xml
	res/xml/led_control_active_screen_settings.xml
	src/com/ceco/gm2/gravitybox/GravityBox.java
	src/com/ceco/gm2/gravitybox/ledcontrol/ActiveScreenActivity.java
	src/com/ceco/gm2/gravitybox/ledcontrol/LedSettings.java
	src/com/ceco/kitkat/gravitybox/ModLedControl.java