Bug 26143: Make the API handle per_page=-1

Bug 26143: Make the API handle per_page=-1

This patch introduces handling for per_page=-1 and actually adds a
missing feature to the API: being able to request all resources on a
route.

To test this:
1. Visit the libraries admin page
2. On the table, choose to display 'All' rows
=> FAIL: it doesn't refresh, the browser console displays a 500 error
code and so the logs
3. Apply the tests patches
4. Run:
   $ kshell
  k$ prove t/Koha/REST/Plugin/Pagination.t \
           t/db_dependent/Koha/REST/Plugin/Objects.t
=> FAIL: Tests fail loudly
5. Apply this patch
6. Restart plack
7. Repeat 2
=> SUCCESS: choosing to display all, works
8. Repeat 4
=> SUCCESS: Tests pass now!
9. Sign off :-D

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>