Migration of discogs scripts to version 2 of discogs_client module.
Version 1 doesn't work anymore since it used webservice endpoints that
have been removed:
http://www.discogs.com/forum/thread/521520689469733cfcfd2089#53a9fd48ad9d3529d0bd28d4
[discogs_cover_art] Handle releases with multiple release events.
[wp_wikidata_links] Handle instrument and series too.