Add drag events to DragablzItemsControl

[mgnslndh]

It would be nice to have drag events on the DragablzItemsControl so that you can use "event-to-command" binding in MVVM scenarios and let the view model get notified.

Today I have to use AddHandler on the view to add a routed event handler and manually invoke the command on the view.

In my specific scenario I use the control to order items by dragging them in the desired order. I am interested in the DragCompleted event so that I can commit the order of items to their view models.