Make Docker Helper more scripting friendly

[jkuester]

What feature do you want to improve?
The docker-helper script is great for spinning up test CHT instances. However, it only works via a prompt-based CLI. As discussed in medic/cht-conf#620 (comment), it would be nice to update the docker-helper to make it easier to script with.

Describe the improvement you'd like

More discussion/investigation is needed to determine the best approach, but some of the proposed ideas are:

• Add support to the script for passing some arguments to the initial call that will bypass the prompts
• Break out certain functionality into into well-defined sub-scripts that could be independently consumed
• Rewrite into JavaScript
• Move the whole docker-helper into cht-conf