Performance settings: remove dithering setting

This setting has no effect in CM10.2, as SurfaceFlinger has now been
taught to automatically Do The Right Thing [tm] with regards to deciding
when to enable surface dithering.

Change-Id: I67fba732440507c1209f2793d826badd4b4d34d5
Settings: ensure SystemSettingCheckBoxPreference defaultValue is set

Change-Id: If2a6234ad78e7b03de86f72e866633817cf888c5
Fix broken target icon.

Steps to reproduce:
- Assign an icon from file
- Save
- Reopen lockscreen targets
- Assign a resource icon
- Save

Result: You'll get the application icon, because the icon file reference
is still present, but the file is no longer there.

Change-Id: I8851f5fbdebfeeef9459c5b44c599e489b2dda3a

Conflicts:

	src/com/android/settings/cyanogenmod/LockscreenTargets.java
Check for presence of hardware abstraction framework.

Change-Id: I59da970d4a4eb74a571d1ac27cb18e351dfc2a53
PORT: Button backlight settings