Revert "Light settings: reduce tone if preview image color is very light"

This reverts commit 5867afb123972ec05782551652f6b9469222b6e2.
Revert "Remove lights settings unless intrusive LED bools are true"

This reverts commit 7cfd5ab8380ce11180156e3bc4742cb78cad114b.
Revert "[2/2] Settings: Battery and Notification Lights"

This reverts commit 30c2b05f0051994f672f72f2153f69a334667c63.

Change-Id: Iac8c9ea8ccbfe33b1fb82415ef8a8fe3c07d9eb1
Revert "Introduce SystemSettingsCheckBoxPreference"

This reverts commit 3223e2d7b2eca1629b3466de0de4a8c31e5f3415.
Add back a helper pref that holds a system setting.

Change-Id: I7d8978829bde1f1dd15bf59f464557f64aa07beb