Coordinate values of backend and frontend can now exchange precision

An understanding of precision has been added to the backend's GeoCoordinateValue and the frontend's
GlobeCoordinateValue::newFromJSON will now use it instead of calculating some default precision
each time.

Change-Id: Id2ee9ba6e2da80b1cd521ba0bbe54e21d32bc6c2
Merge "Coordinate values of backend and frontend can now exchange precision"