Integrate supervisord

[truemped]

At least the Workers and Log Sink should be supervised and automatically restarted. In addition rework the spyder.masterprocess and spyder.workerprocess to daemonize nicely.

[rosner]

Scrapy (https://github.com/scrapy/scrapy) supports start and stop and thelike for different spiders/crawlers. I believe this is interesting for working with MultihostFrontiers.