Add a reverse_geocode function to tiger geocoder

[robe]

Given a PostGIS long/lat WGS 84/NAD 80 geometry point (and an optional option of returning the street range (for cross streets) - boolean that defaults to false), return an array of approximate street addresses and other related items (reverse interpolating along the edges and street address ranges).

Other related items would be an array of cross streets (this will include street range if include_street_range is tru), array of centerline points (if the point is say at the corner of 2 streets) would return the interpolated centerline points) or just one.

This will be useful for example managing fleets of cars or emergency response when you get back a long lat from GPS devices, but don't know where that is along your road networks or if its parked off the street or possibly at a site)