Make the JSON model over the API control be the correct casing & make Mads happy :)

src/Umbraco.Web/Models/ContentEditing/RollbackVersion.cs

@@ -1,13 +1,18 @@
 using System;
+using System.Runtime.Serialization;
 
 namespace Umbraco.Web.Models.ContentEditing
 {
+    [DataContract(Name = "rollbackVersion", Namespace = "")]
     public class RollbackVersion
     {
+        [DataMember(Name = "versionId")]
         public int VersionId { get; set; }
 
+        [DataMember(Name = "versionDate")]
         public DateTime VersionDate { get; set; }
 
+        [DataMember(Name = "versionAuthorName")]
         public string VersionAuthorName { get; set; }
     }
 }