Improve Process Documentation With Up-To-Date Process Images

[hhund]

We should add a mechanism that automatically generates PNG or SVG graphics from BPMN files. This would allow us to integrate them in README.md files or the process Wiki. This could also be used for generating images if we decide to create a GitHub Pages website, alternatively we might want to use a bpmn-io/bpmn-js to directly display BPMN files in HTML.

We could use a node based docker image with the bpmn-io/bpmn-to-image package to create PNGs and SVGs during the maven build via fabric8io/docker-maven-plugin