Fixed requirements, remote-job tracking.

I'm not sure this is necessary since Postgres can handle foreign key references back to the same table without needing to `use_alter`. Can you reconfirm it works without this change?

Also, SQLAlchemy's autogenerated constraint name is `networklink_parent_id_fkey`, so using `fk_networklink_parent_id` will break existing deployments in a future migration script.