define engine API/rpc interface (make engine callable)

[mwartell]

Currently the launcher/loader

1. reads an experiment
2. gathers all the necessary resources
3. launches an image with resource mounts
4. passes the experiment to the container as a shell command
5. retrieves the standard out from the container

Because the mounts in (3) assume a local unix platform, this means that the container must be run on localhost. Also,
the narrow stdin/stdout communication with the container forces us into a batch oriented run. That is, niceties like interacting with the armory run is impossible.

We are looking at the way Jupyterlab connects to its compute kernel to see if we can break the batch-orientation.

[mwartell]

Per today's stand-up, @christopherwoodall will be looking at the Jupiterlab/kernel interface protocol for ideas.