Revert "Brings performance settings up-to-date with cm-10.2"

This reverts commit 78c05083ba8b386d7d86e4ee708f41a07a43dc1c.
Revert "Settings: Forward port Performance settings"

Change-Id: Ib510b35fc2763c6942737afa33873aa5d349a173

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 (reverted from commit 4b604ae317908cb3668f79302bd1a710131b4e0d)