Use GeoJSON in JSON and GML in Atom to represent geo types

Right now we use a common literal format based on "Well Known Text" for literals within URLs, serializing in ATOM, and serializing in JSON.

Well-known-text defines a convenient format for URLs, yowever, both Atom and JSON have "native" representations of geo types. The most natural representation in ATOM is the xml representation GML. GeoJSON appears to be the most broadly accepted way to encode geo types in JSON. It works very well in JSON.

It would be unfortunate to force consumers in XML or JSON to have to understand formats that are not common in each environment, and unfortunate to have extra brackets or curly braces in URLs