Bug 29939: Use the REST API for ratings

Bug 29939: Use the REST API for ratings

This patch replaces opac-ratings-ajax.pl with a new REST API route
POST /public/biblios/42/ratings

Note that we could go further and refactor the 'start_rating' select
code.

Test plan:
Test the "star ratings" feature at the OPAC, on the different page
where it's displayed.

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>