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
dslv: use new fb fiter method

Change-Id: I00eb8d30eb5f647ca7a0e27e3a99f9c1d04d9e78
Merge branch 'jb4.3' of https://github.com/SlimRoms/packages_apps_Settings into HEAD