Introduce NamedHotkey type.

OpenRA.Game/FieldLoader.cs

@@ -273,6 +273,10 @@ namespace OpenRA
 
 				return InvalidValueAction(value, fieldType, fieldName);
 			}
+			else if (fieldType == typeof(NamedHotkey))
+			{
+				return new NamedHotkey(value, Game.Settings.Keys);
+			}
 			else if (fieldType == typeof(WDist))
 			{
 				WDist res;