Use SystemSettingSwitchPreference.

Change-Id: I14fe1c9b1c5ead1ddb20c61ba080bb005f2130d7

Conflicts:
	res/xml/blacklist_prefs.xml
	src/com/android/settings/cyanogenmod/SystemSettingCheckBoxPreference.java
Add back a helper pref that holds a system setting.

Change-Id: I7d8978829bde1f1dd15bf59f464557f64aa07beb