Added dynamic wrapper support to IFileSystem to allow context specific implementations from which to hang extension methods upon (ie IMediaFileSystem)

src/Umbraco.Core/IO/IMediaFileSystem.cs

@@ -0,0 +1,11 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace Umbraco.Core.IO
+{
+    [FileSystemProvider("media")]
+    internal interface IMediaFileSystem : IFileSystem
+    { }
+}