Dispatcher be more resilient

[kailuowang]

basically, it should be able to recover from unexpected children death - queueProcessor, queue, metricsCollector, authThrottler, etc To improve metrics collector it needs to be an actor under the dispatcher hierarchy - see #161.

[nsauro]

?

[kailuowang]

basically, it should be able to recover from unexpected children death - queueProcessor, queue, metricsCollector, authThrottler, etc

[kailuowang]

For 0.4.0, it seems that the only supervision we can improve without major refactoring is the supervision against autothrottle. To improve metrics collector it needs to be an actor under the dispatcher hierarchy - see #161. So I am going to reschedule this to 1.0RC

[kailuowang]

It's blocked by #192