generate grant-settings scripts per user and database

instead of one script setting all grants, a set of scripts should be placed in /var/lib/postgresql/grants. Layout: /var/lib/postgresql/grants: |-db1 | |-user1.sql | |-user2.sql |-db2 | |-user1.sql | |-user2.sql |-set_grants set_grants should accept a list of DBs for which all scripts are applied. If a grant file changes, it should be appied.