Support SSH Authentication for Docker Container Driver

As of docker `18.09` you can connect to a remote docker daemon over SSH without actually exposing the daemon socket and/or configuring TLS certs. (see https://docs.docker.com/engine/reference/commandline/dockerd/#daemon-socket-option)

e.g. `docker -H ssh://remoteip ps -a`

It would be fantastic if support for this could be added into the Docker driver.

Cheers

Start by locating the Docker driver and its existing connection handling. Use the Docker SSH example in the issue as the behavior to investigate, then determine how support should be exposed and verified; the issue does not name specific files or tests.

Written by the indexing model from the issue text.