Revert "HALO: Keep floating app in recents and disable transparent layer temporarily"

This reverts commit f047ec21de58f44e2a7fbe3b597104b98fd0543a.
Recents: Clear all button for recent apps.

An icon will appear on navbar when there are apps available to be killed on recent apps.

Credits to @BigBrother1984 for kitkat porting from jellybean

Patchset 2: Tablet mode is deprecated now, so no need of multiple callbacks
Patchset 3: Remove copyright from unaffected files
Patchset 4: Remove unused imports

Change-Id: I93d1d4cb34325190b03ae3a0d40e1bc170c92d91

Conflicts:

	packages/SystemUI/src/com/android/systemui/recent/RecentsHorizontalScrollView.java
	packages/SystemUI/src/com/android/systemui/recent/RecentsPanelView.java
	packages/SystemUI/src/com/android/systemui/recent/RecentsVerticalScrollView.java
	packages/SystemUI/src/com/android/systemui/statusbar/phone/NavigationBarView.java
HALO: Keep floating app in recents and disable transparent layer temporarily

Change-Id: I01a96d4b1bd8aa8b37829116f1cbda7c7adf84a8