enable augur to detect its own full collection/idle task state and shut down

[MoralCode]

It may be useful for testing purposes to add an option (via a special command line flag or config option or something) to have augur stop and shut itself down once it hits full collection and all tasks go idle.

this would be intended for instances with VERY few small repos (1-5) that are being run in a CI-like environment, such as for automated end-to-end testing (as is the usecase for the parent issue)

[MoralCode]

shutting down may be difficult specifically on docker unless the docker stack running augur is set to a restart policy that doesnt automatically restart (i.e. not always, on-failure or unless-stopped).

while generally written, this also might effectively be a docker-only usecase since bare metal instances dont relaly fundamentally work with a "run it in CI" workflow