Clear all in recent apps and memory usage in recent apps

Clear all on recent apps original code from PA D4rKn3sSyS

Screenshot is here :
https://twitter.com/htchoi1995/status/290835833144086528

Signed-off-by: htchoi1995 <htchoi1995@gmail.com>

Conflicts:
	packages/SystemUI/src/com/android/systemui/recent/RecentsPanelView.java