Implement better handling of default time limits for Device and DeviceSet.
Implement better shutdown of DeviceWrapper and ActorWrapper (still some work to do somewhere,
since MirrorDevice still complains at shutdown).
Improve CommandQueue so that the "run next" callback is added after other callbacks,
making for a cleaner sequence, easier-to-read logs, and eliminating needless calls to runQueue
when a queued command is purged.