UUID.Guid needs a public setter after all because of limitations in XmlSerializer

At some point we may switch to DataContractSerializer which is much more flexible

LibreMetaverseTypes/UUID.cs

@@ -37,7 +37,7 @@ namespace OpenMetaverse
     public struct UUID : IComparable<UUID>, IEquatable<UUID>
     {
         /// <summary>The System.Guid object this struct wraps around</summary>
-        public Guid Guid { get; internal set; }
+        public Guid Guid { get; set; }
 
         #region Constructors