Derek furst/datasets feature revisions

[yuanzhou]

Following the merged PR #229 but for TEST

[yuanzhou]

@DerekFurstPitt has tested on DEV, ready to move to TEST:

Found a published dataset. Created a new dataset and left "previous revision uuid" as that published dataset. When going to datasets/<id>/revision I correctly get back "2". When I go to /datasets/<id>/revisions I get the 2 datasets in order of newest first (as is desired). If I send the same request without authorization, I only get back the published dataset and the next_revision_uuid field is missing. I think its working correctly