Add GPL modules

MediaBrowser.Controller/Entities/ISupportsBoxSetGrouping.cs

@@ -0,0 +1,12 @@
+
+namespace MediaBrowser.Controller.Entities
+{
+    /// <summary>
+    /// Marker interface to denote a class that supports being hidden underneath it's boxset.
+    /// Just about anything can be placed into a boxset, 
+    /// but movies should also only appear underneath and not outside separately (subject to configuration).
+    /// </summary>
+    public interface ISupportsBoxSetGrouping
+    {
+    }
+}