Replacing MemoryPack and BinaryFormatter with MessagePack, which covers a much wider range of .net frameworks

Removed all old Serialization tags and methods
Potentially Breaking Change: Removed InventoryNode.ParentID - This was an old serlization hack. Use Data.ParentUUID instead

LibreMetaverse/Formatters/UUIDFormatter.cs

@@ -0,0 +1,31 @@
+using MessagePack;
+using MessagePack.Formatters;
+using System;
+using System.Buffers;
+using System.Collections.Generic;
+using System.Text;
+
+namespace OpenMetaverse.Formatters
+{
+    public class UUIDFormatter : IMessagePackFormatter<UUID>
+    {
+        public static readonly UUIDFormatter Instance = new UUIDFormatter();
+
+        public void Serialize(ref MessagePackWriter writer, UUID value, MessagePackSerializerOptions options)
+        {
+            writer.Write(value.GetBytes());
+        }
+
+        public UUID Deserialize(ref MessagePackReader reader, MessagePackSerializerOptions options)
+        {
+            var sequence = reader.ReadBytes();
+            if (sequence == null)
+            {
+                throw new MessagePackSerializationException("Invalid UUID");
+            }
+
+            var bytes = sequence.Value.ToArray();
+            return new UUID(bytes, 0);
+        }
+    }
+}