Slim recents: Add favorite mode

Conflicts:
core/java/android/provider/Settings.java
packages/SystemUI/src/com/android/systemui/slimrecent/RecentPanelView.java

Allow user to set favorite apps in recent task list. User can set them with
longpress on the app icon. This apps are always shown in the task list above
the first default one (on phone the first 2 which always show the last 2 active
tasks). Favorites are shown in order of last time they were called. Favorites
settings are saved permanently till the user removed it from favorites.

As well this commit fixes the wrong icon if an package has more then one
activity to call (eg Google+ and Google Photo).

Using for all now a unique identifier.