SystemUI: simpler RAM bar implementation

Change-Id: I6b7c74c515b07269fa2ed9a96263fc47e58d5920
Signed-off-by: Roman Birg <romanbirg@gmail.com>

Conflicts:
	packages/SystemUI/src/com/android/systemui/recent/RunningState.java
RAMBar - show available memory in the old way

Old way means handle cached memory like it was free, subtract it from total.
Also use the internal MemoryInfo class instad of reading from /proc/meminfo.

Change-Id: I96462ed5f1b6923ec8fc4405b225d57691dd1aa0
Signed-off-by: Gergely Szell (sethyx) <szell@hu.ibm.com>