CE-1103 Enable WikiaInYourLang extension on all wikias

Per Yoko request the WikiaInYourLang extension is going site-wide. That requires a tweak that retrieves "vanilla" domain of a wikia without its language prefix (e.g. retrieves pad.wikia.com from zh.pad.wikia.com).

Corresponding config PR: https://github.com/Wikia/config/pull/756
Rather than including manually, just set `$this->setupFile` to the path here, i.e. `$this->setupFile = __DIR__ . '/../WikiaInYourLang.setup.php';`.