"Clear all" button on recent apps

Port forward from cm-10.2

Change-Id: I9ebcf22f85957f61caefb14e0efd4cf2978d92cd

Conflicts:
	packages/SystemUI/src/com/android/systemui/recent/RecentsHorizontalScrollView.java
Fix "no recent apps" color

RIP #33b5e5

Change-Id: Iae5948e224d06023962e43f905756017b42f0637