Merge mbpseudo into musicbrainz

# Conflicts:
#	beetsplug/musicbrainz.py

Author: asardaes

.github/CODEOWNERS

@@ -4,4 +4,3 @@
 # Specific ownerships:
 /beets/metadata_plugins.py @semohr
 /beetsplug/titlecase.py @henry-oberholtzer
-/beetsplug/mbpseudo.py @asardaes