Bug 11620: Add dissertation-information index for MARC21 (502)

Bug 11620: Add dissertation-information index for MARC21 (502)

Bug 11202 introduced a new index 'dissertation-information' for
UNIMARC. This patch adds the index also for MARC21 installations.

http://www.loc.gov/marc/bibliographic/bd502.html

To test:
- Apply patch
- Copy files in etc/zebradb changed by this patch to your
  corresponding directory (koha-dev..)
- Make sure you have records with 502
- Reindex
- Verify you can search the field contents with
  dissertation-information= and
  diss=

Signed-off-by: Bernardo Gonzalez Kriegel <bgkriegel@gmail.com>
Can find by dissertation-information,
No errors

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@unc.edu.ar>