Bug 30402: Import authorities subroutines to ImportBatch script

Bug 30402: Import authorities subroutines to ImportBatch script

The following authorities subroutines are used by the ImportBatch
script but are not accessible, because they aren't imported. This
caused MARC importing errors.
- GetAuthorityXML
- ModAuthority
- DelAuthority

These affected the BatchCommitRecords and BatchRevertRecords routines,
and it wasn't caught because there are no tests written for them.

To test:
1. Find an existing authority record, or import one to use.
2. Save this authority record (export/download).
3. Go to Admin -> Record matching rules. Create a new record matching
   rule for authorities that matches on 001, Local-Number index.
4. Go to Tools -> Stage MARC for import. Upload the authority file you
   just downloaded.
5. Change record type to authority.
6. Under 'Look for existing items in catalog?', set the record matching
   rule to the rule you just made which matches on 001. If matching
   record found, replace the existing one. If no match is found, ignore.
7. Stage the record. Once complete, a match should've been found.
8. Go to Staged MARC management.
9. Import the batch into the catalog. Notice it hangs and never
   completes.

10. Apply the patch and restart services.
11. Repeat steps 4-9. This time importing should be successful.

Sponsored-by: Educational Services Australia SCIS
Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>