Replace obsolete 'site_admin_required' decorator

This allows 'common_utils.py' to no longer depend on the 'security' module.
Add APIv2 endpoints for ImageStore
Inbox delivery for new PTIFF images
Merge branch 'ptiff-session-inbox'

* ptiff-session-inbox:
  Inbox delivery for new PTIFF images
  Add APIv2 endpoints for ImageStore
  Replace obsolete 'site_admin_required' decorator