Fix persisting of multiple associations
Before, selecting multiple artists when creating a new artwork did not persist
any to the db.
Also minor changes.
Keep only the chosen associations
Without this custom logic, "editing" the artist list just adds to it.
Add support for artworks with multiple artists
Before, it only displayed the first artist.
This also decouples it from MySQL commands.
Merge branch 'enable_inverse_persisting' into develop
Merge branch 'multiple_artist_support' into develop
Merge branch 'develop'
Add enhancements, improve look