[2/2] Settings: Doze (ambient display) timeout

Patchset: put the preference in more sensible location.

Patchset: remove preference for devices that don't support
        doze display state.

Patchset: turn off doze timeout slider if doze is disabled

Patchset: move doze options to own preference category

Change-Id: I366a3a00bb48c20fa2d37f0b22fdbfeb3d004533

Conflicts:
	res/values/du_strings.xml
	res/xml/display_settings.xml
	src/com/android/settings/DisplaySettings.java