Issue: Class Proxy System Like XenForo

As some add-on developers have complained, especially XenForo add-on developers, it is not possible to extend many VaultWiki core classes if needed by the add-on -- at least not without requiring vault/config.php changes, and not without interfering with other similar add-ons.

In the next release, VaultWiki will feature a class proxying system similar to the system XenForo uses. The system can be accessed using new effect locations vw_load_controller, vw_load_model, and vw_load_view through your forum software's existing plugin system and creating the plugin normally.

The vw_load_* events work similarly to XenForo's load_class events, but there are some slight differences in the code contents for VaultWiki:
Your class should be defined as follows (using controller-type as an example), in vault/plugins/controller/my/class/vw.php:
Say you want to add different versions for vBulletin, XenForo, etc that extend from your existing plugin. Create vault/plugins/controller/my/class/vb3.php:
Note that due to limitations in vBulletin 3 and 4, many classes are not available for extension all the time, because they might already loaded before vBulletin boots up. Examples include vw_Route_Controller, vw_User_Model, vw_Settings_Model, vw_Datastore_Model, vw_Start_Model, and more.

These limitations do not exist in XenForo.

However, regardless of forum platform, you cannot extend vw_Hard_Core, vw_Dependency_Model, or other classes that are instantiated outside of vw_Hard_Core::fetch_object.