Bug 26999: Make 'Any library' translatable when placing a hold

Bug 26999: Make 'Any library' translatable when placing a hold

This patch makes the 'Any library' string translatable, by converting it
into a flag and using it accordingly on the request.tt template.

To test:
1. Have the 'Hold pickup library match' set to 'any library' on the
   circultation rules.
2. Open the page to place a hold on a biblio with some items
=> SUCCESS: The item says 'Any library' on the 'Allowed pickup
locations' column.
3. Apply this patch
4. Repeat 2
=> SUCCESS: No behavior change
=> SUCCESS: The string is on the template
5. Sign off :-D

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>