Internal visiblility

[LokiMidgard]

I noticed that I implemented AssemblyVisible only for classes. enum and interfaces are still public.

This change should fix that, but one of the new tests fails because of SourceUri property is empty string on attributeGroupRef. I don't think this has something todo with the changes I did. But parse operation in the test that I use wrong.
The xml from the text comes from a project where it is working, so that should be fine.

If someone can give me a hint what I need to change so the last test passes I would appreciate that.

[LokiMidgard]

The Exception occurs here

XmlSchemaClassGenerator/XmlSchemaClassGenerator/ModelBuilder.cs

Lines 464 to 467 in 05c4e33

	if (_configuration.GenerateInterfaces)
	{
	CreateTypeModel(new Uri(attributeGroupRef.SourceUri), AttributeGroups[attributeGroupRef.RefName], attributeGroupRef.RefName);
	}

Message: System.UriFormatException : Invalid URI: The URI is empty.

[mganss]

The SourceUri is empty at this point because the source comes from a string, not an actual uri (i.e. file). There were several places where we just blindly new'ed up a Uri. I've added a helper method CreateUri that takes null and empty strings into account.