Add the themes configuration entry point

Change-Id: I0eb669956d9e89bb92cd43487b14b4246454a400

Conflicts:
	res/values/strings.xml
	res/xml/settings_headers.xml
CPU Settings: add ability to enable/disable ROM preferences
Users can now choose if they want to control the CPU settings
listed below natively or with a 3rd party app.

- CPU governor
- CPU minimum frequency
- CPU maximum frequency
- I/O scheduler for main block device