Cleanup: Use a helper class for system setting binary toggles.

Change-Id: Iad7f8a6bf85b23223e1def18e8c9eaa0f8dd253c

Conflicts:
	res/xml/button_settings.xml
	res/xml/quick_settings_panel_settings.xml
	res/xml/status_bar.xml
	src/com/android/settings/DisplaySettings.java
	src/com/android/settings/cyanogenmod/ButtonSettings.java
	src/com/android/settings/cyanogenmod/NotificationDrawer.java
	src/com/android/settings/cyanogenmod/QuickSettings.java
	src/com/android/settings/cyanogenmod/StatusBar.java