PostGIS 2.0+ allows creation of table in single step

[andyjefferson]

In PostGISAdapter we enforce a two step process, as per the docs for PostGIS 1.x ... namely create a normal table, then call AddGeometryColumn on each spatial column to add them. With PostGIS v2.0+ this is apparently not necessary. See http://postgis.net/docs/manual-2.0/using_postgis_dbmanagement.html#Create_Spatial_Table