Bug 15437: (follow-up) Move $i subfield display to the beginning and add OPAC

Bug 15437: (follow-up) Move $i subfield display to the beginning and add OPAC

This patch builds on Caitlin's to finish the work but keeping as
much from her code as possible.

- Finishes reindenting started in first patch
- Readds a space after the label
- Moves $i to the beginning of the field as suggested by MARC21
  documentation:
  http://www.loc.gov/marc/bibliographic/bd76x78x.html
  The data in subfield $i can be displayed preceding the other
  data contained in the field.
- Adds a span with a class around the $i so people can control
  the formatting

To test:
  - Catalog a record with 780/785 with and without $i.
  - Verify that they display nicely in staff and OPAC, $i should show.
    Also $a and $t will show (unchanged by this patch)

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>