Add support to register internal classes

[dariogriffo]

I cannot register internal classes.
I tend to not expose classes outside the containing assembly, so usually they are

public interface IA {}
internal class A : IA {}

if I decorate A is not added to the registry

[kzu]

As shown in #111, this is fully supported.

Perhaps there's something else going on?

[kzu]

Closing due to lack of response