Create slim Docker image

[ddeboer]

• Create slim image beside the current full one: the slim image should not include PostgreSQL.
• Split development (build-essential etc.) and production images
• Add Dockerfile to 0.x branch, too.

@CyBeRoni Any ideas how to create proper production images that don’t include build tools? Of course, to create a deployable container, we do need the tools.

[ddeboer]

Let’s use something like the dev image I created for Driebit.