UIHANDLER OnReceiveDrag

Called whenever the user has released the cursor over the frame while dragging something.
== Arguments ==
; self : Widget - the widget receiving the drag event.
== Details ==
* The widget must be to receive drag events.
* You can use to find out whether it was an item, spell, macro, or amount of money, and the specifics thereof. 
* The cursor is not automatically cleared; call if that behaviour is desired.
* The handler also fires when dragging widgets onto other widgets, in which case provides no relevant information.