MyCyma

[fix] check artwork properties/subobjects better before displaying

[evol] an artwork can have multiple materials

[fix] renamed 'technique' into more appropriate name 'artwork_support', and update schema and translations (Closes #4)

[evol] add complete user management interface #2

[evol] add complete user management interface

[fix/evol] forgot new files in the previous commits and check admin status to access user management

[evol] updated URLs in 'About' submenu

[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)

[cosmetic] center artwork image in their frame in the arwork admin list

[fix] worked around artwork list default sort not enforced