settings: bring back volume key cursor control

Framework part seems to have survived the merge.

Move volume key cursor control from language & input
to button settings.

Change-Id: Ice2b266e8fdbcdf805d36d8f2e335b569e57be65

Conflicts:

	res/values/cm_arrays.xml
	res/values/cm_strings.xml
	res/xml/button_settings.xml
	src/com/android/settings/cyanogenmod/ButtonSettings.java