ModelBackedItem had no actual utility anymore

SabreTools.Metadata.DatItems/Machine.cs

@@ -10,7 +10,7 @@ namespace SabreTools.Metadata.DatItems
     /// Represents the information specific to a set/game/machine
     /// </summary>
     [JsonObject("machine"), XmlRoot("machine")]
-    public sealed class Machine : ModelBackedItem<Data.Models.Metadata.Machine>, ICloneable, IEquatable<Machine>
+    public sealed class Machine : ICloneable, IEquatable<Machine>
     {
         #region Properties
 
@@ -382,6 +382,15 @@ namespace SabreTools.Metadata.DatItems
 
         #endregion
 
+        #region Private Fields
+
+        /// <summary>
+        /// Internal model
+        /// </summary>
+        private Data.Models.Metadata.Machine _internal;
+
+        #endregion
+
         #region Constructors
 
         public Machine()