Possible missing DataType.json schema

[csuwildcat]

I was running a verbose schema ref compiler on the schemas in the repo and it produced an error stating it could not find DataType.json, which is $ref'd in the Observation.json schema. The DataType.json schema appears to be missing from the list of schemas in the repo, so I wanted to check if I was doing something wrong or if it was just an errant omission.