- removed support for PUIDs and Echoprint
- removed the 'artists' include for work lookup
- allow the 'work-level-rels' include for recording lookups
- added support for 'target-credit' elements
- update valid search fields
- use https by default with musicbrainz.org
python-musicbrainzngs is required only by beets and quodlibet which are built with python3.
Signed-off-by: Algent Albrahimi <email@example.com>