The IDragInitiator interface is the basic interface for the object that
wants to know if a drop was accepted in a drag/drop operation.
There are two methods instead of the usual one because in some scenarios
the drag initiator needs to prepare the data before it gets dropped.
For example, in a tree control, dragging from one node to another,
the tree should un-parent the node before it is moved to the
new parent node, so the tree would un-parent the node in acceptingDrop.