Bug 22347: Translatability of ILSDI GetAvailability

Bug 22347: Translatability of ILSDI GetAvailability

Some discovery tools can't translate ISL-DI results, it would be useful
if we can get ISL-DI output already translate.

This patch add an optional parameter language to GetAvailability, and
make GetAvailability results translatable.
If no parameter is given the output language is the language of the
cookies is present or the first language in the opac language list.

Test plan:
1. Enable the ILS-DI system preference
2. Locate a record
3. Test these URLs:
   [OPACBASEURL]/cgi-bin/koha/ilsdi.pl?service=GetAvailability&id=[BIBLIONUMBER]&id_type=biblio
   and
   [OPACBASEURL]/cgi-bin/koha/ilsdi.pl?service=GetAvailability&id=[ITEMNUMBER]&id_type=item
   (Where the [OPACBASEURL] is the OPAC URL of your test instance,
   [BIBLIONUMBER] and [ITEMNUMBER] are a record number and item number of
   your choice.)
4. Apply the patch
5. Test these URLs:
   [OPACBASEURL]/cgi-bin/koha/ilsdi.pl?service=GetAvailability&id=[BIBLIONUMBER]&id_type=biblio&language=[LANGUAGE]
   and
   [OPACBASEURL]/cgi-bin/koha/ilsdi.pl?service=GetAvailability&id=[ITEMNUMBER]&id_type=item&language=[LANGUAGE]
   (Where the [OPACBASEURL] is the OPAC URL of your test instance,
   [BIBLIONUMBER] and [ITEMNUMBER] are a record number and item number of
   your choice, [LANGUAGE] is a language code ex: 'en' or 'fr-FR')
6. The results should now be in the requested langugage

Sponsored-by: University Lyon 3
Signed-off-by: Sonia <sonia.bouis@univ-lyon3.fr>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>