Start creating Dictionary-based internal models

SabreTools.Models/Internal/Feature.cs

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+using System.Xml.Serialization;
+using Newtonsoft.Json;
+
+namespace SabreTools.Models.Internal
+{
+    [JsonObject("feature"), XmlRoot("feature")]
+    public class Feature : DatItem
+    {
+        #region Keys
+
+        /// <remarks>string</remarks>
+        public const string NameKey = "name";
+
+        /// <remarks>(unemulated|imperfect)</remarks>
+        public const string OverallKey = "overall";
+
+        /// <remarks>(unemulated|imperfect)</remarks>
+        public const string StatusKey = "status";
+
+        /// <remarks>(protection|timing|graphics|palette|sound|capture|camera|microphone|controls|keyboard|mouse|media|disk|printer|tape|punch|drum|rom|comms|lan|wan)</remarks>
+        public const string FeatureTypeKey = "type";
+
+        /// <remarks>string</remarks>
+        public const string ValueKey = "value";
+
+        #endregion
+
+        public Feature() => Type = ItemType.Feature;
+    }
+}