split gb_postcode in table creation and data loading

Data for gb_postcode now needs to be downloaded first.
Also fixes table creation for postgis 2.0.

data/gb_postcode_table.sql

@@ -0,0 +1,27 @@
+-- This data contains Ordnance Survey data © Crown copyright and database right 2010. 
+-- Code-Point Open contains Royal Mail data © Royal Mail copyright and database right 2010.
+-- OS data may be used under the terms of the OS OpenData licence:
+-- http://www.ordnancesurvey.co.uk/oswebsite/opendata/licence/docs/licence.pdf
+
+SET statement_timeout = 0;
+SET client_encoding = 'UTF8';
+SET standard_conforming_strings = off;
+SET check_function_bodies = false;
+SET client_min_messages = warning;
+SET escape_string_warning = off;
+
+SET search_path = public, pg_catalog;
+
+SET default_tablespace = '';
+
+SET default_with_oids = false;
+
+CREATE TABLE gb_postcode (
+    id integer,
+    postcode character varying(9),
+    geometry geometry,
+    CONSTRAINT enforce_dims_geometry CHECK ((st_ndims(geometry) = 2)),
+    CONSTRAINT enforce_srid_geometry CHECK ((st_srid(geometry) = 4326))
+);
+
+GRANT SELECT ON TABLE gb_postcode TO "www-data";