PEEK (2/2)

- Toggle PEEK On/Off
- Make PEEK and LN working togheter as different options
- Put a explanation abaout how these 2 fatures work together

Based on (with some modifications): https://github.com/AOSPA/android_packages_apps_Settings/commit/db85f442ab46ac74011a63f4fb5adc5c3c01df4f
Thanks  to: @BigBrother1984

Change-Id: Ic5496765a3e4a72750588feaf7488415d8292337

Conflicts:
	res/values/cr_strings.xml
	res/xml/lockscreen_interface_settings.xml
	res/xml/lockscreen_notifications.xml