Copied tests from MIRA
commit: https://github.com/curationexperts/mira/commit/3a891ad8808774581a6cf2f689cf3325a374dca4
Copy in test from mira
From commit:
https://github.com/curationexperts/mira/commit/3c52f6664ca9a9f684cea3e184e208b611914b90
Remove art & art history fixtures from test list
Move personal and course collections into tufts_models
added method to get positions of members
made flattened_member_ids_with_collections ignore deleted members
added explicit local namespace
When updating a datastream that doesn't have the local prefix, add it. Fixes curationexperts/tufts-image-library#52
Remove external datastreams from new fixtures
Ensure the dcmi namespace (ac prefix) is added to documents that don't already have it. Ref #295