Remove unused thumbs API
Remove unused / deprecated DataSessionItemsAPI from APIv1

The attachment API functionality has been superseded by APIv2, and all
client-side calls to the attachment API use APIv2.

The views / images API functionality was never implemented, and there is
no client side code that calls it. New views / images functionality will
be implemented in APIv2.
Move all sessions to admin database

Simplify session list template.
Add disambiguating label field to APIv2 users list
Update APIv2 to use Flask-Restful
Rename "organization" to "collection"
Fix session editor to work with collections
Merge branch 'session_in_admin'

* session_in_admin:
  Fix session editor to work with collections
  Rename "organization" to "collection"
  Update APIv2 to use Flask-Restful
  Add disambiguating label field to APIv2 users list
  Move all sessions to admin database
  Remove unused / deprecated DataSessionItemsAPI from APIv1
  Remove unused thumbs API