Misc housekeeping

These popped up while testing the trait documentation extraction.

OpenRA.Mods.Common/Traits/Tooltip.cs

@@ -21,11 +21,13 @@ namespace OpenRA.Mods.Common.Traits
 	}
 
 	[Desc("Shown in map editor.")]
-	public class EditorOnlyTooltipInfo : TooltipInfoBase
+	public sealed class EditorOnlyTooltipInfo : TooltipInfoBase
 	{
-		public override object Create(ActorInitializer init) { return this; }
+		public override object Create(ActorInitializer init) { return new EditorOnlyTooltip(); }
 	}
 
+	public sealed class EditorOnlyTooltip { }
+
 	[Desc("Shown in the build palette widget.")]
 	public class TooltipInfo : TooltipInfoBase, ITooltipInfo
 	{