Add nullable context to SabreTools.DatItems

This change also starts migrating the internals of the DatItem formats to the new internal models. Right now, it's basically just acting like a wrapper around those models.

SabreTools.Models/Internal/DictionaryBase.cs

@@ -93,6 +93,9 @@ namespace SabreTools.Models.Internal
             if (asArray != null)
                 return string.Join(',', asArray);
 
+            // TODO: Add byte array conversion here
+            // TODO: Add byte array read helper
+
             return this[key]!.ToString();
         }
 

SabreTools.Models/Internal/RamOption.cs

@@ -8,6 +8,9 @@ namespace SabreTools.Models.Internal
     {
         #region Keys
 
+        /// <remarks>string</remarks>
+        public const string ContentKey = "content";
+
         /// <remarks>(yes|no) "no"</remarks>
         public const string DefaultKey = "default";
 

SabreTools.Models/Listxml/RamOption.cs

@@ -13,6 +13,9 @@ namespace SabreTools.Models.Listxml
         [XmlAttribute("default")]
         public string? Default { get; set; }
 
+        [XmlText]
+        public string? Content { get; set; }
+
         #region DO NOT USE IN PRODUCTION
 
         /// <remarks>Should be empty</remarks>