* We can use setDropItem:dropChildIndex: to reposition the drop.
*
* @param outlineView The outline view which will receive the drop
* @param info The NSDraggingInfo
* @param item The item into which the drag would currently drop
* @param index The index within item into which the drag would currently drop. It may be a 0-based index inside item or may be NSOutlineViewDropOnItemIndex.