MyCyma

[evol] preliminary artworks context menu (reverted license to GPL2+, to be compatible with Proto.Menu and possibly other plugins)

[evol] added tags and fixes a few typos

[evol] added more links from artwork steps to the artwork

[fix] ensure the default display size for a thumbnail (currently the full image) does not crash (closes #77)

[fix] handle image/thumbnail errors better in helpers

[fix] ensure ArtworkStep has a non-nil/NULL 'position' (not set in ArtworkStepThumbnail for example)

[evol] added helper methods for ArtworkStep<Image|Thumbnail>

[fix] tries to regen missing thumbnail

[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)

[cosmetic] use first artwork image instead of last for set thumbnail in the tree view (closes #17)