Additional settings for "AcousticBrainz tags"

[natrius]

Follow-up for https://github.com/metabrainz/picard-plugins/issues/269 as there is now a settings-page but some settings would be usefull

• "join multiple values with: '; / '" or something like that. Let us choose like other plugins are doing currently
• "Ignore genres" with a list separated by new line or semikolon for some weird genres or moods someone doesn't like/need.