Add NATS.io-compatible worker queue

[sneakycrow]

We want to re-add the worker queue feature, but done using NATS.io as the backend as opposed to the former Postgres implementation

[sneakycrow]

#57 Cleaned this up a bit more. All we need is for the job_runner to be able to process events with the subject farmhand.jobs.>, and re-add the processing logic itself.

I think this can be considered feature complete once we can process video streams again, end to end