Bug 8332: Add relationships to auth_finder for authority links

Bug 8332: Add relationships to auth_finder for authority links

In addition to the work in bug 8207 that enables auth_finder use, it
would be very useful when creating authorities to have the auth_finder
plugin automatically fill out the relationship information in $w (in
MARC21).

To test (note that you must either apply the patch for bug 8207 or
manually add a thesaurus to a 5xx linking field in one of the authority
type frameworks):
1. Create a new authority record.
2. Go to the 5xx tab.
3. Click the authority control plugin ellipsis.
4. Do a search for an authority.
5. Select a relationship type.
6. Note that after you choose an authority, that the $w control field
   is automatically populated with the relationship type.

Signed-off-by: Frédéric Demians <f.demians@tamil.fr>
After applying patch for bug 8207, I had been able to follow the test plan step
by step, and get the expected result.

Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com>
Rebased on master 1 August 2012