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/config.xml
settings: Remove ZRAM settings

 * Android has proper ZRAM support builtin now, and this code doesn't
   even work. Remove it.

Change-Id: I39cb20809d5c71683bffc578057ad39363c5066e