Support Super+[Number] for Launching Dockitems [$35]

I find that the Super+[Number] shortcuts in Unity are very useful in bringing up favourite applications quickly. Ubuntu's shortcuts work top to bottom; similarly, in Plank they can go from left-to-right (or top-to-bottom in vertical docks), with Super+1 launching the first item, Supet+2 the second item, and so on.

These shortcuts will reduce the need for mouse movements and make life easy for both new users and users migrating from Ubuntu Natty, Oneiric or Precise.