Gaufrette adapter - rename method

[rmsint]

Currently not implemented, see https://github.com/symfony-cmf/MediaBundle/blob/master/Adapter/Gaufrette/CmfMediaDoctrine.php#L230

Should we rather throw an Exception? Or introduce a capabiltiies API.

public function __construct()
{
$this->addCapability(self::CAN_RENAME);
$this->addCapability(self::CAN_REMOVE);
$this->addCapability(self::CAN_WRITE);
// whatever
}

[rmsint]

I think we look at this after 1.1, when we also will look at the integration with SonataMediaBundle