HOVER: Option to exclude topmost app [1/2]

Originally taken from Tigger2014:
https://github.com/Tigger2014/android_frameworks_base-1/commit/5af0e1c84e86e9b4e6947163aaf58e9ab541079d

Change-Id: I6da9027af4c7bc74945a06b97b876f94cf817844

Conflicts:
	core/java/android/provider/Settings.java