Removing the SearchDropTarget bar as it no longer contains the QSB

> Renaming it to simply DropTargetBar
> Moving AppInfo to the top bar as well
> The workspace pages will extend to the top edge (minus some padding).
Since the QSB is no longer displayed on top of every page, there is
no reason to reserve the space.
> In spring-loaded mode, the workspace cell layout will scale enough
to make room for the drop target bar at the top

Change-Id: I2baf607310335dd576c9d9fcbb75ab708f47ac03