Get data from fedora-tagger rather than using the canned FAS data

The FAS data does not exist anymore and so cannot be refreshed. We will only
refresh the fedora-tagger ratings data at the most every 3 months as they should
change little in this time and we don't want to kill the single server.
Only get the rating data when required

This speeds up startup by about 25ms as we only need the ratings data for the
details page and for sorting the search results.