Derivatives:simple should support multi-page items

[mnyrop]

• use openseadradon for simple derivatives (see: Openseadragon for IIIF ~and~ simple image viewing. wax#56)
• derivatives:simple should create an array of images to add to collection page front matter IF the item is paged
• derivatives:simple should use the first image for main thumbnail and full banner 🐛

Edit: These changes in wax_tasks would be best written into a v2.0 that makes use of tmp and state-tracking json files so that the array of paged derivatives & their variants can be captured without writing that info back into a cannonical CSV.

Time to rip the band-aid off! 🩹⏲️