Use the actual IDs for Musicbrainz resources
We were generating internal unique IDs for Musicbrainz resources, which looked like this:
The actual Musicbrainz URL is already guaranteed to uniquely represent the resource, so let's use that to identify the resource inside Tracker. This means the URL is shorter, more readable, and can be browsed. The above example becomes this:
This shouldn't be backported to the stable branch.