Bug 20006: Adapt /holds to the RFC

Bug 20006: Adapt /holds to the RFC

This patch makes the /holds endpoint respect the voted RFC. Some
behaviours are changed as well:

- As we voted to introduce a /public namespace for unprivileged access to
endpoints, this endpoint gets the ability for owners and guarantors to
manipulate holds through the API.

- GET /holds now uses the objects->search helper, so it now has
pagination.

To test:
- Apply this patches
- Run:
  $ kshell
 k$ prove t/db_dependent/api/v1/holds.t
=> SUCCESS: Tests pass!
- Sign off :-D

Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>