Check datatype for date format conversion

Closes #3199
-If datatype is dateTime convert to javascript Date object when
 retrieved from the database.
-Add tests to make sure models and internal API are using Date
 objects for dateTime fields.
-Add tests to make sure the HTTP API is returning ISO 8601
 date strings for dateTime fields.
Merge pull request #3201 from jaswilli/issue-3199

Check datatype for date format conversion