bring back DPI changer - AOKP

PS4:Added situation that values don't exists in build.prop

Change-Id: I3e3a63eb64b0f107c1fad0f2fd8bb7c7f6e6e227
Signed-off-by: ChampionSwimmer <android@championswimmer.tk>

Conflicts:
	src/com/aokp/romcontrol/fragments/UserInterface.java