v1.0.20

Many thanks to @bassstorm and @Lovecraft-github !

Change log:

What´s new:

• Track artists used for VA release search instead of Album artist (requires album/tracks with 'Album artist' equal or prefixed by 'VA' or 'Various' - #109).
• Experimental feature: VA artist artwork download (#96).
• Export tag mappings as JSON.

Fixes:

• Close Preview dialog after writing tags.
• Do not throw fatal error loading 404 artist previews.

Notes:
The experimental VA release image downloads feature is limited to artwork download (not file tagging).