Revision 2460

(PostgreSQLServer.execute_sql): Extend to
so that it returns a result for select statements.
(PostgreSQLServer.server_version): New.  Return the version of the
server software.
(PostgreSQLServer.require_authentication): The format of
pg_hba.conf has changed between PostgrSQL 7.2 and 7.3.  Check the
server version and generate the file in the correct format