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>

Conflicts:
	res/values/cm_arrays.xml
	res/values/cm_strings.xml
	res/values/config.xml
	res/xml/performance_settings.xml
	src/com/android/settings/cyanogenmod/BootReceiver.java
	src/com/android/settings/cyanogenmod/PerformanceSettings.java
Settings: QS performance profiles tile

Requires http://review.cyanogenmod.org/#/c/51776/

Credit: CM

Patchset 2: Fix not null comparation
Patchset 3: Added suggestions
Patchset 4: Fix string
Patchset 5: Rebased
Patchset 6: Rebased
Move setCurrentValue() inside mPerfProfilePref null check
settings: add auto power profiles option

Credit: CM