Add ClrMamePro deserialization test, fix issues

SabreTools.Models/ClrMamePro/MetadataFile.cs

@@ -0,0 +1,18 @@
+namespace SabreTools.Models.ClrMamePro
+{
+    public class MetadataFile
+    {
+        /// <remarks>clrmamepro</remarks>
+        public ClrMamePro? ClrMamePro { get; set; }
+
+        /// <remarks>game, machine, resource, set</remarks>
+        public GameBase[]? Game { get; set; }
+
+        #region DO NOT USE IN PRODUCTION
+
+        /// <remarks>Should be empty</remarks>
+        public string[]? ADDITIONAL_ELEMENTS { get; set; }
+
+        #endregion
+    }
+}