[WIP] Docker cleanup

Currently working at breaking the Docker stuff out a bit more.

This will include:

- [ ] Creating a separate culling script (non-web facing) that just queries the proxy's metadata
- [x] Renaming `rando.py` to `orchestrate.py`. I'm open to naming suggestions.
- [x] Fixing a current intermittent bug when a container doesn't exist for some reason

I'd like to see the actual spawner be separate from the outer endpoint, so the tornado application that handles the `/spawn` route doesn't actually have pure access to the Docker socket (or root).
This is a separate Python file all together, no main yet (though I want the culler as a standalone).

However, for orchestrate (below), you're saying I should put this in `__main__`?