Feature/sr sln 680 daemonization

Basic daemonization.

I'm close to what I consider a bare minimum feature set, I can never do everything in the TODO.txt in the time I have, but I think that defaulting cluster size to number of cpus, and having SIGINT and SIGTERM do a .shutdown() of all workers (aka graceful close) are my remaining mandatory things to make it credible. After that, we can drive feature priority by what is useful in terms of driving features to the strongops dashboard, or with feedback from users.

@rmg   If there is something you think MUST be there to use this to run apps under strong-agent/cluster-control, that would be useful feedback.

@bnoordhuis I'm interested in any comments you have, and specifically if I'm overlooking some aspects of daemonization, or misusing or just not noticing useful node/cluster APIs/features. I haven't run tests on windows, but I will have to, so portability is of interest, too.