add fail xml import on subject not unique exception option

It will help address this problem...

> Following track1 to update a grouper db 1.3.1 to 1.4.0
> https://wiki.internet2.edu/confluence/display/GrouperWG/v1.4+Release+No
> tes.
>
>
> After import is complete, groups that were members of other groups are
> no longer. The member-groups show up later in the xml file than their
> parent. Is that why import did not assign them as members?
>
> If so, is there a way for the export to order the groups? Could the
> import read the whole file first? Am I out of luck for ever being able
> to import?