Add private docker registry

[vigevenoj]

These links have an overview of what's required:
http://imhotep.io/k8s/docker/2016/08/04/docker-registry.html
http://container-solutions.com/running-secure-registry-kubernetes/
https://blog.cloudhelix.io/using-a-private-docker-registry-with-kubernetes-f8d5f6b8f646
https://phvu.net/2017/01/27/secured-private-docker-registry-in-kubernetes/

So we'll need the image from hub.docker.com/_/registry/ , add a htpassword entry, tls cert and key that we use to secure the registry... or the phvu link suggests fronting the built-in registry with nginx for ssl. I think traefik could be used for that part.