Subdivide SQL function to prepare for improved error handling The context of an error (e.g. the function in which it occured) can be inferred by the database client. Not doing all in one statement will render the context more meaningful.

The gemma database schema requires PostgreSQL >= 11.

`dot.tmpl` is a template file for `postgresql_autodoc`
to be more similiar to UML and leave out some less useful labels.

See  `../docker/README.md`