Allow non-public types in registry

[tomasaschan]

Currently, lambda closure types may cause problems for an AssemblyEventRegistry with the default namer func (type => type.Name), since they all get the name <>c and thus throw exceptions when trying to add several types with the same name to the dictionary (see #12).

An intermediate workaround is to include only public types in the registry, but this is more limiting than it has to be - it would be nice to figure out a way to support any type, or at least any user-generated type.