Include DeclaringType.Name for nested types when generating explicit implementation names

[JelleKerkstra]

This PR resolves the DynamicProxyException Duplicate element: Castle.DynamicProxy.Generators.MetaMethod when generating a proxy that implements the following interfaces due to the nested classes.
In the current implementation, only the namespace, type name and method name are considered. In this PR, the declaring type names are also used when generating explicit interface implementations due to matching method names.

public static class OuterWrapper
{
	public static class InnerWrapperA
	{
		public interface ISharedName
		{
			void M();
		}
	}

	public static class InnerWrapperB
	{
		public interface ISharedName
		{
			void M();
		}
	}

	public static class InnerWrapperC
	{
		public interface ISharedName
		{
			void M();
		}
	}
}