Simple Composite Actor cannot be dragged onto display
The simple, empty 'Composite Actor' does not appear in the actor tree because it
has been 'commented out' in the actorList.moml file. Uncommenting it makes it
appear in the actor tree, but then dragging it to the right to place it in a
workflow creates an error! ("Property is not an instance of Attribute...").
Being able to simply create a Composite Actor by dragging it to the work area
seems to be fairly important.