MBS-6270, add track identifier redirect and rdfa attributes.
MBS-6270, use URI object to add fragment identifier in Controller::Track.

(also other small cleanups to that file, based on pull request feedback).
MBS-6270, add Data::Release->find_gid_for_track test.
MBS-6270, Add Controller::Track test.
MBS-6270, highlight the requested track if a track identifier appears as the fragment on a release page.
MBS-6270, redirect to /recording/:mbid if a /track/:mbid is a permalink to a pre-ngs track.
Merge branch 'mbs-6270' into beta

* mbs-6270:
  MBS-6270, redirect to /recording/:mbid if a /track/:mbid is a permalink to a pre-ngs track.
  MBS-6270, highlight the requested track if a track identifier appears as the fragment on a release page.
  MBS-6270, Add Controller::Track test.
  MBS-6270, add Data::Release->find_gid_for_track test.
  MBS-6270, use URI object to add fragment identifier in Controller::Track.
  MBS-6270, add track identifier redirect and rdfa attributes.