Start creating Dictionary-based internal models

SabreTools.Models/Internal/Port.cs

@@ -0,0 +1,21 @@
+using System.Xml.Serialization;
+using Newtonsoft.Json;
+
+namespace SabreTools.Models.Internal
+{
+    [JsonObject("port"), XmlRoot("port")]
+    public class Port : DatItem
+    {
+        #region Keys
+
+        /// <remarks>Analog[]</remarks>
+        public const string AnalogKey = "analog";
+
+        /// <remarks>string</remarks>
+        public const string TagKey = "tag";
+
+        #endregion
+
+        public Port() => Type = ItemType.Port;
+    }
+}