Bug 31796: Add REST endpoint to modify an authority

Bug 31796: Add REST endpoint to modify an authority

To test:
1. Apply patch
2. Set RESTBasicAuth preference to true
3. Pick an authority to modify, and modify it's marc record
4. Make a PUT request to /api/v1/authorities/:authid with one of the following content type header
  - application/json
  - application/marcxml+xml
  - application/marc-in-json
  - application/marc
5. If content type is other than 'application/json' place the following header in the request 'x-authority-type: <auth type>'
5. Check that the authority was modified
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>