Support controllers out of bundles

Need this to support [bundleless application code][1]. Currently using [my own bundle][2] for that, but would be nice to have this in the bundle itself.

[1]: http://elnur.pro/symfony-without-bundles/
[2]: https://github.com/elnur/ElnurTemplateGuesserBundle
Didn't know that. I saw that some docs use FQCN, e.g.: https://github.com/symfony/symfony/blob/master/src/Symfony/Bridge/Doctrine/DependencyInjection/AbstractDoctrineExtension.php#L316, https://github.com/symfony/symfony/blob/master/src/Symfony/Bridge/Doctrine/Security/RememberMe/DoctrineTokenProvider.php#L51