Sitecore spatial geojson polygons

Implementation of a Linq extension to be able to query on points that intercept GeoJson polygons in Solr indexes. The demo provides a template with the spatial field, a couple of sample items with polygons from OpenStreetMap that cover some cities; and a controller rendering that reads lat and long from the query string and returns the polygon of the item found (e.g. Big Ben's coordinates return London).