Mulgara

Create a registry object for EmbeddedMulgaraServer to set pass out to any services that it starts up.

I was initially tempted to go with a dictionary, but I prefer the idea of keeping a tighter control on the information passed around. We can always expand what's held in the registry, but it will be centralized, rather than having services work on an ad hoc basis.

The reason this needs to be a registry and not a set of parameters is because objects may need to be passed to services after they have been created. The canonical example here is where the framework creates a SessionFactoryFactory, along with the web servlets, but until the startup phase there is no instance of Database - which is what the web servlets need. For the moment, each service is holding a handle to EmbeddedMulgaraServer and queries that object directly, but the internals of this class need to be kept away from all the objects it creates.