Add hideable kill-all-button to recent switcher (1/2 FWB part)

original code done by Robin Morawetz for my IceColdSandwich ROM

Change-Id: Iaa59b337d4d16cadf003abbe34f4c1870f8c0cd4

Conflicts:
	core/java/android/provider/Settings.java
	packages/SystemUI/res/layout-port/status_bar_recent_panel.xml
	packages/SystemUI/res/values/strings.xml
	packages/SystemUI/src/com/android/systemui/recent/RecentsPanelView.java