[evol] added set view and linked it from tree view
[evol] created display_artwork_frame() helper function and now use it in the welcome page + created a set/group tree view with it too
[evol] use SQL sessions instead of cookies-based ones
[evol] language can be forced in the user admin page (closes #6) (no user interface yet)
[fix] renamed 'technique' into more appropriate name 'artwork_support', and update schema and translations (Closes #4)
[evol] redirect to home page after logout, instead of login page
[fix/evol] forgot new files in the previous commits and check admin status to access user management
[evol] created a simple logon system, protected admin pages, and added a logon indicator/link (no user management yet, only a deadend entry in the menu if admin)
Initial version