Move PostgreSQL dockerfile to separate repository with automation for publishing or sibedge/postgres-plv8 docker image instead

[konard]

We should move https://github.com/deep-foundation/deeplinks/blob/deeplinks-70-menzorg/postgresql/dockerfile to separate file.

This docker image was done when #70 was in progress, and this docker image now is published in deepf account of DockerHub and used in https://github.com/deep-foundation/hasura repository.

Or we should use existing https://hub.docker.com/r/sibedge/postgres-plv8 docker image or other compatible one.