FEATURE: CORE-2204 - Add polygon and point as new datatypes to DataSpace

QA: This API isn't used by the frontend currently so there shouldn't be any UI-facing changes to test.
Incorporating Evan's CR comments
Improving the coordinate precision to 12 decimal places per discussion with Colin and Franklin.

Reviewed-by: evan.chan@socrata.com
Address CR comments from Evan
Replace Line and Polygon with MultiLine and MultiPolygon

Reviewed-by: evan.chan@socrata.com
Address Evan's CR comments