Automate running DB-tests with an extra database run_tests.sh allows to run database tests easily without affecting other existing databases and on a clean basis. Because roles are cluster-wide, they cannot be easily droped and recreated without affecting other databases. Thus, moved their creation to roles.sql and in passing removed unnecessary role 'gemma'.

--
-- Primary GEMMA roles
--
CREATE ROLE waterway_user;
CREATE ROLE waterway_admin IN ROLE waterway_user;
CREATE ROLE sys_admin CREATEROLE BYPASSRLS IN ROLE waterway_admin;