Multivalue tags (ex. Genre)

[natrius]

https://www.guayadeque.org/viewtopic.php?t=183

Add support for multivalue tags, tagged with semilkolon separated values, for example the genre. It can be done with Musicbrainz Picard automatically pretty good and Foobar2000 (good player for Windows) is supporting it as well for example.

EDIT: Ideally let the user choose with what the mutlivalue-tags are separated because its possible to choose in musicbrainz as well. Otherwise i personally would prefer ; because its already supported by foobar2k