Add softwarelist deserialization test, fix issues

SabreTools.Models/SoftwareList/Software.cs

@@ -36,5 +36,17 @@ namespace SabreTools.Models.SoftwareList
 
         [XmlElement("part")]
         public Part[]? Part { get; set; }
+
+        #region DO NOT USE IN PRODUCTION
+
+        /// <remarks>Should be empty</remarks>
+        [XmlAnyAttribute]
+        public XmlAttribute[]? ADDITIONAL_ATTRIBUTES { get; set; }
+
+        /// <remarks>Should be empty</remarks>
+        [XmlAnyElement]
+        public object[]? ADDITIONAL_ELEMENTS { get; set; }
+
+        #endregion
     }
 }