add option to force high-end graphics on low memory devices

Change-Id: I34e0d7381615485b58385abed743e01f7272772d
Merge remote-tracking branch 'cm/cm-11.0' into cm-11.0

Signed-off-by: Chester Kener <Cl3Kener@gmail.com>

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