Add an optional parameter to enable generation of internal interfaces

[mtren]

No description provided.

[simonmckenzie]

This is a copy of the logic inside GetNameSpace:

net_automatic_interface/AutomaticInterface/AutomaticInterface/Builder.cs

Lines 80 to 89 in 0ed9589

	private static string GetNameSpace(ISymbol typeSymbol)
	{
	var generationAttribute = typeSymbol
	.GetAttributes()
	.FirstOrDefault(x =>
	x.AttributeClass != null
	&& x.AttributeClass.Name.Contains(AutomaticInterfaceGenerator.DefaultAttributeName)
	);
	if (generationAttribute == null)

Could you perhaps extract the attribute retrieval logic into a separate method and retrieve it once, passing it to both GetNameSpace and GetAsInternal?

[ChaseFlorell]

I think I have already covered this in #77 and adding the internal logic to the GeneratedSymbolDetails should likely be pretty straight forward.