Add the themes configuration entry point

Conflicts:
	res/values/mahdi_strings.xml
	res/xml/customization_settings.xml
Add new themes items to personalization menu

Bring in logic for the new chooser. If TMO chooser is installed it will get
first priority.

Change-Id: Ia8e852e5e5ad2465d0b9b73f16c7080a7337bb8a

Conflicts:
	res/values/mahdi_strings.xml
	res/xml/settings_headers.xml
	res/xml/theme_settings_slim.xml

Conflicts:
	AndroidManifest.xml
	res/values/purity_strings.xml
	res/xml/settings_headers.xml
Add missing mdpi, hdpi, xhdpi drawables for new theme engine

Change-Id: I70dd75257f0e3a0a20b844a1ea3cc36506de177b