[draggable] Add Actor prerequisite
[draggable] Add Actor prerequisite

A NbtkDraggable must be a ClutterActor, so we need to add the
prerequisite in the type definition.

clutter-project/mx,clutter-project/mx,jonnylamb/mx,pwithnall/mx,jonnylamb/mx,pwithnall/mx,clutter-project/mx,jonnylamb/mx,pwithnall/mx,clutter-project/mx,pwithnall/mx,jonnylamb/mx