Retrive the calculated revision number of a Dataset. The calculated revision is number is based on the [:REVISION_OF] relationships to the oldest dataset in a revision chain. Where the oldest dataset = 1 and each newer version is incremented by one (1, 2, 3 ...). Public/Consortium access rules apply, if is for a non-public dataset and no token or a token without membership in HuBMAP-Read group is sent with the request then a 403 response should be returned.