[cosmetic] display groups in a set into a light blue cell, like in the tree (closes #18), and btw improved CSS handling a bit (unfinished)
[cosmetic] invert arwork list and group list in set view (refs #18)
[evol] added artwork view and now use the new image frame in all views
[evol] added group view and linked it from the tree and set views
[evol] added set view and linked it from tree view