Migrated section controller + LanguageTreeController, ApplciationTreeController.

Updated AngularJsonOnlyConfigurationAttribute to be a TypeFilterAttribute, to allow injeciton into the filter.

Note: Left TODO about checking authorization of proxied trees..

src/Umbraco.Web.Common/Extensions/FormCollectionExtensions.cs

@@ -4,9 +4,8 @@ using System.Linq;
 using System.Text;
 using Microsoft.AspNetCore.Http;
 using Umbraco.Core;
-using Umbraco.Web.Common.Extensions;
 
-namespace Umbraco.Web.Common.Extensions
+namespace Umbraco.Extensions
 {
     public static class FormCollectionExtensions
     {