Exporting nodes from within a group behaves unexpectedly

If you try to export a node that is within an existing node group (that is, tab into an existing node group and then try to use Node > Export to .blend), this add-on doesn't quite function as expected. Currently, it clears out just the other nodes within that group, but nothing in the group's parent tree.

What *should* happen is that the selected nodes should be pulled out of the group to the root of the tree and then all of the other nodes should be removed from there. Of course, this introduces a few complications if you want backlinking to work.