MBS-7749: Rap Genius/Rock Genius to Genius rename

The Rap Genius/Rock Genius sites have been renamed to just Genius,
under the new domain name genius.com (instead of rapgenius.com). They
also have a new logo. This requires updating the URL cleanup and
sidebar icon code.
Merge remote-tracking branch 'chirlu/mbs-7749' into beta

* chirlu/mbs-7749:
  MBS-7749: Rap Genius/Rock Genius to Genius rename