Bug 32735: Add endpoint to list authorities

Bug 32735: Add endpoint to list authorities

This patch adds an endpoint to list authorities

To test:
1. apply patch
2. enable basic auth
3. call to GET /api/v1/authorities with the following Accept headers:
 * application/json
 * application/marcxml+xml
 * application/marc-in-json
 * application/marc
 * text/plain
4. notice how data changes with each Accept header
5. prove t/db_dependent/api/v1/authorities.t
6. sign off

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>