Implements DND for data collections.
| $drag | the method is called when a drag operation is initiated |
| $dragDestroy | called when drag has been completed |
| $dragIn | the method is called when an item is moved into a possible drop landing during dnd |
| $dragMark | called during drag-n-drop, when some item of the component should be marked as an active drop target |
| $dragOut | called when the mouse pointer has been moved out of the drop area |
| $dragPos | defines the position of a dragged item |
| $drop | the method is called when an item is dragged and dropped on a valid target |