Fleshing out virtual collections.

 - add script to create VC content type
 - add VC fixtures
 - add tests for current functionality
Fix display of scopes in permission error
Make virtual collections require a unique id
Add, via the awesome power of copy-and-paste, a VC resource and client test
Merge branch 'master' into virtual_collections
Merge branch 'master' into virtual_collections
Actually we don't need to re-index after adding this node
Merge branch 'master' into virtual_collections
Merge branch 'master' into virtual_collections
Merge branch 'master' into virtual_collections
Rename VirtualCollection to VirtualUnit to reflect its relationshio to DocumentaryUnit
Tweak fixtures to reflect new structure.
VirtualUnit is not a described entity
Merge branch 'master' into virtual_collections