Option to disable wallpaper service

Change-Id: Ia80ae699979a69cdf3497955967df59658cbe5bf

Conflicts:
	res/values/cm_strings.xml
	res/xml/performance_settings.xml
	src/com/android/settings/cyanogenmod/PerformanceSettings.java
Cleanup

Change-Id: I9140b4c7e3c81dc05bca9f57f7c45d10da32e92e