[Reviewer Andy] Dynamic Sproutlet loading

Andy

Can you review the changes for dynamic sproutlet loading.  I'll email updated spec separately.

Mike
This list looks overly generous, in particular, why is the scscf_acr_factory shared across Sproutlets?  I'd expect in general for Sproutlets to instantiate their own instances of helper libraries.

In fact, the only object that I think belongs here is the `LoadMonitor`which is effectively part of the `Sproutlet->SproutBase` API (to allow reporting of service-level latency penalties).