allow DEFAULT_GEOMETRY_FIELD to be configurable in settings + fix bug where GeometryField was called something other than 'geometry'
documentation: view parameter is 'geometry_field_name' not 'geometry_field'
convert GEOS geojson string to dict to avoid double json-encoding, to create valid GeoJSON
Merge pull request #1 from batpad/master

Bugfixes for geometry field name and invalid geojson