Revision 2059

* Thuban/Model/postgisdb.py
(PostGISTable._fetch_table_information): Delegate the creation of
column objects to a different method so that we can extend that in
derived classes
(PostGISTable._create_col_from_description): New. Column object
creation part of _fetch_table_information
(PostGISShapeStore._create_col_from_description): New. Extend
inherited method to handle geometry columns
(PostGISShapeStore.__init__): New parameter geometry_column to
specify which geometry column to use.  Optional but mandatory for
tables with more than one geometry column
(PostGISShapeStore._fetch_table_information): Also use the name of
the geometry column when looking for the srid
(PostGISShapeStore.ShapeType): Also use the name of the geometry
column when looking for the shape type

* test/test_save.py (SaveSessionTest.test_save_postgis): Adapt
NonConnectionStore to changes in the PostGISShapeStore

* test/test_postgis_db.py
(TestPostGISSpecialCases.test_shapestore_two_geom_cols): Test
PostGISShapeStore with tables having two geometry columns.