WIP: Automate the building of the tutorial container

Created by: scottwittenburg

Similar to how it was originally done here:

https://github.com/scottwittenburg/sc2019-tutorial-pipeline

Still TODO:

• Pick the right set of apt packages to install in the container
• Come up with tagging scheme to be used in the item below
• Set up the DockerHub auto-build (thinking to use tag source type with regex feature)
• Document how DockerHub auto-build is set up
• Decide on whether to keep the keyhelp directory with it's shell script for exporting a gpg key in various ways for use in the container as well as in the pipeline (if you name a key that has an associated passphrase, it won't work in the build jobs)
• Once this PR is mostly ready, we can close it and open a new one on the same branch to trigger the pipeline to run again, pointing at the new mirror which will have just the pkgs we want in the final container.