DriverChain defaultDriver

The \Doctrine\ORM\Mapping\Driver\DriverChain is a good thing, but a default driver should be a another great thing.

Actually, to use DoctrineExtension Translatable I have to use the DriveChain to add a specific driver for Gedmo\Translatable.
The problem is, that I have to define the same EntityDriver on all my entity in this driver.

$driverChain->addDriver ($entityDriver, 'EntityA');
...
$driverChain->addDriver ($entityDriver, 'EntityB');
$driverChain->addDriver ($translatableDriver, 'Gedmo\Translatable');

It would be really friendly to do
$driverChain->setDefaultDriver ($entityDriver);
$driverChain->addDriver ($translatableDriver, 'Gedmo\Translatable');

I have attach a fix (SVN) for the DriveChain class.