Move geocoder to central site

[nick]

We now have a geocoder (source:trunk/npemap.org.uk/cgi/geocoder.fcgi), which works off our data, and returns the best match it can find (exact, outer+1 inner, outer, area), as plain text or xml

We need to move this onto the central site, since it's better suited there than on just npemap

Depending on how long that'll take, we may wish to advertise it in the mean time.