jBPM server distribution using docker

As a jBPM community member, I would like to quickly get started to evaluate the toolkit capabilities for designing, deploying and running business projects using docker.

Acceptance criteria:

• A docker image is provided on Docker Hub which assembles all needed services including kie-server, jbpm-console, case management showcase, similarly to the server (single zip) distribution.
• Link to docker image is provided in the jbpm.org download page.
• CI is properly setup to support delivering the image in future releases.
• A blog post is included in the jbpm.org website including how to use the docker image.
• N&N section in docs is updated to include relevant information about the new image.