Bug 12842: Add DDC classification numbers to MARC21 XSLT detail page

Bug 12842: Add DDC classification numbers to MARC21 XSLT detail page

Patch will add DDC classifications, divided with | below the subjects
in the OPAC and staff detail pages.

To test:
- catalogue a record with one or mulitple 082$a subfields
- verify the classifications are displayed in OPAC and staff detail page
- Add following CSS to OpacUserCSS or IntranetUserCSS:

.results_summary.ddc {
  display:none;
}

- Verify the DDC classifications are now no longer displayed

Signed-off-by: Frederic Demians <f.demians@tamil.fr>
Test plan ok. Repetions of $a subfield are separated by a space, which seems
correct. I'm not sure whether other subfield than $a should be displayed on
intranet. Whatever, this could be added later.

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