[evol] artworks context menu: finished mechanism + checked for empty selection + implemented associate_with_tag action
[evol] added tags and fixes a few typos
[cosmetic] added position number to artwork_step_images, only visible in the admin pages, to be able to change order for steps made the same day (closes #16)
[fix] work around steps order when done at the same date (considering people would add them in chronological order) using image id
[evol] an artwork can have multiple materials
[fix] renamed 'technique' into more appropriate name 'artwork_support', and update schema and translations (Closes #4)
Initial version