Starts fixing up the doc type folders stuff, fixes permissions settings on the trees, adds error messaging for duplicating folders, removes the click handler for folder nodes

src/Umbraco.Web/WebApi/HttpRequestMessageExtensions.cs

@@ -11,6 +11,7 @@ using System.Web.Http;
 using System.Web.Http.ModelBinding;
 using Microsoft.Owin;
 using Umbraco.Core;
+using Umbraco.Web.Models.ContentEditing;
 
 namespace Umbraco.Web.WebApi
 {
@@ -107,6 +108,22 @@ namespace Umbraco.Web.WebApi
             return msg;
         }
 
+        /// <summary>
+        /// Creates an error response with notifications in the result to be displayed in the UI
+        /// </summary>
+        /// <param name="request"></param>
+        /// <param name="errorMessage"></param>
+        /// <returns></returns>
+        public static HttpResponseMessage CreateNotificationValidationErrorResponse(this HttpRequestMessage request, string errorMessage)
+        {
+            var notificationModel = new SimpleNotificationModel
+            {
+                Message = errorMessage
+            };
+            notificationModel.AddErrorNotification(errorMessage, string.Empty);
+            return request.CreateValidationErrorResponse(notificationModel);
+        }
+
         /// <summary>
         /// Create a 400 response message indicating that a validation error occurred
         /// </summary>