Make the built-in wiitdb files optional

There are some cases where overriding the opening.bnr names
isn't desirable, such as when someone has several modded
versions of a game that differ in names but not game IDs.

Source/Core/Core/ConfigManager.h

@@ -257,6 +257,7 @@ struct SConfig : NonCopyable
   bool m_InterfaceLogConfigWindow;
   bool m_InterfaceExtendedFPSInfo;
   bool m_show_active_title = false;
+  bool m_use_builtin_title_database = true;
   bool m_show_development_warning;
 
   bool m_ListDrives;