Bug: frontend 500 error on `Lang::Dictionary()->translate($str);`

I was just trying to implement this extension but my front-end craps out with a 500 error.

The error message is: `PHP Fatal error:  Call to a member function translate() on a non-object in /..my-project../extensions/cookie_law/data-sources/data.cookie_law.php on line 61`

It seems the `Lang::` class is unknown. Is this only a matter of `require`ing the `lang/lang.xx.php` file?
