Add ctrl-agent to the image(s)

The images should have:

• ctrl-agent installed and running
• have its port exported, probably with HTTP only
• it should be documented how to enable TLS for the control-agent

Or perhaps the container come with TLS as a default and fail to run, unless certs are provided? This would make them more difficult to set up initially, but would be more secure long term. Not sure what's the Docker practice is.