"Clear all" button on recent apps

Change-Id: I9ebcf22f85957f61caefb14e0efd4cf2978d92cd

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

recents: Move Clear All button to bottom left

Only in portrait mode. I think it actually looks
better / is more accesible in the top right in landscape.

PS2: Fix derp

Change-Id: I61f9df3660656994c3cc0df1fc5744b6669b4361
Signed-off-by: Andrew Warfield <hiasant@gmail.com>