Image subcommands for "Antidote" tool

[Mierdin]

Currently the antidote tool doesn't include any subcommands for images. I'd propose adding three:

"list" and "get"

Would be nice to have an antidote command to list and get images from a curriculum, so at-a-glance, contributors can see what images are available to them to use.

Should also consider if it's feasible to allow people to view this information on a repository they haven't even cloned yet. Doing this on a cloned repo is table stakes of course, but would be interesting if we had an option to check an "online" repo so that we can let users list the images for a given curriculum using only a few commands. Maybe a "remote" flag that, if provided affects both commands. If not provided, defaults to looking at local directory.

"create"

Following what's already done with collections and lessons, run the user through a wizard and create files for them. Might want to consider adding Dockerfile and Makefile (just templates) as well (if so, please update docs).