[M] (DI-2-3) (DI-4-1) Revisit the pgsphere postgis issue

[lawrence]

To make sense of geographical searching of our data we need to do better than simply use the bounding box "within" command. Ideally we should be able to expose some operators (e.g. "encloses" which would allow us to define global = encloses (80S,80N) and handle global and smaller datasets differently. that way we could use googlemaps effectively, without doing so it is difficult to see how one would do it.