Determine list of SEBA containers from charts

Given a set of helm charts and a variable file, write a script that will create a list of all container images required by those helm charts. If the helm charts or values file changes, this list can be updated by running the script instead of the substantial manual effort to determine the list of containers.

One way this could be done is by running `helm template -f <variable_file>.yaml <chart_dir>`, then parsing out all the container image names.

The list should be either a text file with one image name per line, or YAML if more metadata is needed.