Reuse @style/MmsHoloTheme in sub-activities

By using @style/MmsHoloTheme in sub-activities (like 'Setting') instead of
inheriting from @android there will be more consistency around the app
if a theme developer modifies the main theme (e.g. when inverting the app
colors).

Change-Id: I92851cbe8375d995067e515d2dabdf6d9225a7e5