add custom collection sort orders to edit page

MediaBrowser.Controller/Entities/IHasDisplayOrder.cs

@@ -0,0 +1,15 @@
+
+namespace MediaBrowser.Controller.Entities
+{
+    /// <summary>
+    /// Interface IHasDisplayOrder
+    /// </summary>
+    public interface IHasDisplayOrder
+    {
+        /// <summary>
+        /// Gets or sets the display order.
+        /// </summary>
+        /// <value>The display order.</value>
+        string DisplayOrder { get; set; }
+    }
+}