Extend what is included in IIIF Manifest

• 1. Only include public resources in public manifest (cf Hyku issue 1170)
• 2. Manifest should include (cf Hyku issue 1171):
  • 2.1 images only (phase one) - Hyku PR
  • 2.2 all UV-able resources (phase two)
  • 2.3 user configuration of manifest contents (phase three)

Hyku uses iiif_manifest: https://github.com/samvera-labs/iiif_manifest