Bug 20434: Update UNIMARC framework - script

Bug 20434: Update UNIMARC framework - script

Test plan:
1. Take a look at files in misc/migration_tools/ifla/data. It
   contains all data that will be inserted into Koha. Its content is
   based on the previous patches.
2. Run the script misc/migration_tools/ifla/update.pl and verify
   that it effectively added the new fields, subfields, authorised
   values and authority types.
3. Run the script again and see that it doesn't update existing fields
4. Run with --force and verify that it update existing fields (you can
   modify unimarc_ifla.yml to see changes)
5. Run with --force --po-file misc/migration_tools/ifla/language/fr.po
   and verify that the labels are now in french

There is a POT file in misc/migration_tools/ifla/language/template.pot,
use it to create PO files for other languages.

Signed-off-by: Sonia BOUIS <sonia.bouis@univ-lyon3.fr>
Signed-off-by: Alex Arnaud <alex.arnaud@biblibre.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>