Create Docker image with ready-to-use development environment

Created by: dboehmer

Good example of software project: https://github.com/roschaefer/rundfunk-mitbestimmen#installation-and-usage-with-docker-quick-but-without-software-tests

A interested developer/potential contributor should be able to easily call Docker to obtain a dev environment without any Perl, Coocook or sysadmin knowledge.