Add Performance and memory management to AOSP (from CM)

This is a direct port from the CM10.1 implementation. DVtonder commited it,
the original author may be buried somewhere in gingerbread, I guess.
DVtonder migrated it to settings in CM9.(and wrote it himself, maybe)

Seems to work well enough here.
Change-Id: If42bb3046ca4c9089d7d6a460e187e9e88a747f3

Conflicts:
	AndroidManifest.xml
	res/values/arrays.xml
	res/values/strings.xml