Bug 28948: Add GET /public/libraries routes

Bug 28948: Add GET /public/libraries routes

This patch introduces a route to fetch a list of libraries or a single
library as expected on the /public namespace. It is expected to return
the 'public' representation of the Koha::Library objects.

To test:
1. Apply this patches
2. Run:
   $ kshell
  k$ prove t/db_dependent/api/v1/libraries.t
=> SUCCESS: Test pass and they cover all the cases!
3. Try your favourite REST tool against the new route.
4. Sign off :-D

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>