Migrated HttpQueryStringModelBinder into netcore.

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

@@ -0,0 +1,12 @@
+using Microsoft.AspNetCore.Http;
+
+namespace Umbraco.Web.Common.Extensions
+{
+    public static class HttpRequestExtensions
+    {
+        internal static string ClientCulture(this HttpRequest request)
+        {
+            return request.Headers.TryGetValue("X-UMB-CULTURE", out var values) ? values[0] : null;
+        }
+    }
+}