fix(codegen): Adds string intern, encoded int, enum and legacy version support (#613)

- [X] Adds Enum migration rule
- [X] Adds legacy version (writing full int for version field)
- [X] Adds encoded int attribute
- [X] Adds intern string attribute
- [X] Fixes missing base deserialize/serialize

Projects/Server/Serialization/InternStringAttribute.cs

@@ -0,0 +1,27 @@
+/*************************************************************************
+ * ModernUO                                                              *
+ * Copyright 2019-2021 - ModernUO Development Team                       *
+ * Email: hi@modernuo.com                                                *
+ * File: InternalizeString.cs                                            *
+ *                                                                       *
+ * This program is free software: you can redistribute it and/or modify  *
+ * it under the terms of the GNU General Public License as published by  *
+ * the Free Software Foundation, either version 3 of the License, or     *
+ * (at your option) any later version.                                   *
+ *                                                                       *
+ * You should have received a copy of the GNU General Public License     *
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>. *
+ *************************************************************************/
+
+using System;
+
+namespace Server
+{
+    /// <summary>
+    /// Hints to the source generator that a serializable string field or property should be internalized on deserialization
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Field | AttributeTargets.Property)]
+    public class InternStringAttribute : Attribute
+    {
+    }
+}