Cleanup & Fixes for .NET 5 (#309)

- [X] Fixes several bugs
- [X] Updates more ordinal issues
- [X] Cleans up the code a bit
- [X] Turns classes static that should have been
- [X] Changes TcpServer.Instances to a HashSet

Bumps release version

Projects/UOContent/Engines/Craft/DefBlacksmithy.cs

@@ -1351,10 +1351,12 @@ namespace Server.Engines.Craft
         }
     }
 
+    [AttributeUsage(AttributeTargets.Class)]
     public class ForgeAttribute : Attribute
     {
     }
 
+    [AttributeUsage(AttributeTargets.Class)]
     public class AnvilAttribute : Attribute
     {
     }