Creates a new <code>TreeDragSourceEffect</code> to handle drag effect from the specified <code>Tree</code>.
@param tree the <code>Tree</code> that the user clicks on to initiate the drag
See Implementation
Creates a new <code>TreeDragSourceEffect</code> to handle drag effect from the specified <code>Tree</code>.
@param tree the <code>Tree</code> that the user clicks on to initiate the drag