Bug 18731: /acquisitions/orders endpoint

Bug 18731: /acquisitions/orders endpoint

This patches implement the /acquisitions/orders endpoint.

The attribute names are consistent with the voted RFC

To test:
1. Apply this patchset
2. Run:
   $ kshell
  k$ prove t/db_dependent/api/v1/acquisitions_orders.t
=> SUCCESS: Tests pass!
3. Test the API with your favourite tool (Postman?)
=> SUCCESS: It works as expected!
4 Sign off :-D

Sponsored-by: Camden County
Signed-off-by: Matthias Meusburger <matthias.meusburger@biblibre.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>