Base: Allow hiding notification icons

When long pressing a notification, add another menu
item which allows the user to hide the notification icon
(but keep the actual notification in the dropdown).

This is meant for applications which have services running
in the statusbar which the user is aware of, so right now
we hide the icon by the package.

Change-Id: I60c8705e1fd02d7b26dbe90fe39a3b40febdbfcc
Keep app when opening floating window from recents panel

Start activity asynchronously by appending it to system's
message queue to let RecentsPanelView cleanly execute
dismissAndGoBack before the floating window gets started.

Change-Id: Ie58ddc81b4ea897b4243404a58fae47583e49e1a

Conflicts:
	packages/SystemUI/src/com/android/systemui/recent/RecentsPanelView.java
SystemUI: prevent NPE on clear recents double press

Pressing Clear all button twice fast or while the list
is clearing but not yet fully cleared causes sysui to crash due to
mRecentTaskDescriptions being null: (http://pastebin.com/2gRFvf8k)

Workaround it by hiding clear all recents button.

Change-Id: I23d10edfd336041739fe80352ee01987e671dbd7