* Where $type is 'specialpage', 'parserhook', 'variable', 'media' or 'other'.
* Where 'descriptionmsg' can be an array with message key and parameters:
* 'descriptionmsg' => array( 'exampleextension-desc', param1, param2, ... ),
* Where $type is 'specialpage', 'parserhook', 'variable', 'media' or 'other'.
* Where 'descriptionmsg' can be an array with message key and parameters:
* 'descriptionmsg' => array( 'exampleextension-desc', param1, param2, ... ),