- Add Jobserver.map()
- Add JobserverExecutor, a c.f.Executor implementation wrapping Jobserver
- Hoist preexec_fn, sleep_fn, and env defaults that may apply to all submits
- Add Future.done(..., signal=...) for signal-based canceling of running work
- Name worker processes Jobserver-worker for easier id in process listings
- Fix re-entrant CallbackRaised double-wrapping
- Add 9 worked examples