Documentation: Fixes missing namespaces on class call

[gabidavila]

On http://docs.doctrine-project.org/projects/doctrine-orm/en/latest/reference/tools.html#reverse-engineering there are calls like the following:

$cmf = new DisconnectedClassMetadataFactory();

Which would cause fatal error if not in the namespace call list, however as documentation for this feature already starts with

$em->getConfiguration()->setMetadataDriverImpl(
    new \Doctrine\ORM\Mapping\Driver\DatabaseDriver(
        $em->getConnection()->getSchemaManager()
    )
);

I added the namespace on the calls itself to maintain consistency.

[Ocramius]

@gabidavila thanks! 👍

[gabidavila]

;)