Aggregates Lokad Style ... LANDED!

- For those that want to separate their root entity and their state à la
Lokad (well,  pretty close to that style).
- Streamlined some of the method names and invocation
(IInstanceEventRouter all the things)
- Went overboard, renamed Register to ConfigureRoute, reverted after
sanity came back
- OT: Fixed some of that samplesource nunit assertions stuff that was
still utilizing the DIY approach