Binding: Added None

src/TensorFlowNET.Core/Binding.cs

@@ -7,5 +7,10 @@ namespace Tensorflow
     public static partial class Binding
     {
         public static tensorflow tf { get; } = New<tensorflow>();
+
+        /// <summary>
+        ///     Alias to null, similar to python's None.
+        /// </summary>
+        public static readonly object None = null;
     }
 }