Add the themes configuration entry point

Change-Id: I0eb669956d9e89bb92cd43487b14b4246454a400

Conflicts:
	res/values/strings.xml
	res/xml/settings_headers.xml

Conflicts:
	res/values/strings.xml

Signed-off-by: DHOMD <DHO@dho.im>

Conflicts:
	res/values/strings.xml
	res/xml/settings_headers.xml