SystemUI: Recents window visual updates

* Changed the KillAll button to not have a border/be transparent
* Stretched out the RAM bar across the top, and add a small shadow underneath

PS4: Drop landscape related changes down
     from GNow commit (wrong patch)

maxwen: I dont like the shadow and the stretching - removed

Change-Id: Iabdab0a083b00ee51834415f0454f8298efe5591

Conflicts:
	packages/SystemUI/res/layout-land/status_bar_recent_panel.xml
	packages/SystemUI/res/layout-port/status_bar_recent_panel.xml