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
Settings: Forward port Change behavior when back pressed in PerformanceSettings

When back key pressed, finish this activity if user does NOT accept 'Ok'
in warning dialog rather than show it.
Id: Ied763db4f76a3a2a36f134bd93a0f18047c6cf5c

Change-Id: I07d41d43d00e4fb42ad526d27ee9188d830906ea
Performance profiles

This changes adds support for custom performance profiles through overlays. Supported
devices should define config_perf_profile_prop with the proper system property to be set
and fill an init.rc file with the appropiate handlers for every defined performance profile..
Patchset 2: Rebased
            New simplified strings
Patchset 3: Fix build
Patchset 4: Rebased

Change-Id: I5a6612db94da3c09d8ec2e8920bf9516f62d0024
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>