Got extension methods working for DynamicDocument. Exposes some new APIs publicly because they need to work with type finding and med trust, plus we need to expose these for MVC

src/Umbraco.Core/Models/IDocument.cs

@@ -11,7 +11,7 @@ namespace Umbraco.Core.Models
 	/// A replacement for INode which needs to occur since INode doesn't contain the document type alias
 	/// and INode is poorly formatted with mutable properties (i.e. Lists instead of IEnumerable)
 	/// </remarks>
-	internal interface IDocument
+	public interface IDocument
 	{
 		IDocument Parent { get; }
 		int Id { get; }