Bug 12609 - Replace use of DBI in C4::Ratings with DBIx::Class

Bug 12609 - Replace use of DBI in C4::Ratings with DBIx::Class

Test Plan:
1) Apply this patch
2) prove t/db_dependent/Ratings.t
3) Note all unit tests pass

Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Also tested:
- Adding a rating
- Rating displayed on detail
- Rating displayed on results
- Modifying a rating
- Change displayed correctly on detail and results

Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>