Check AdvancedUserInterface flags at password grant

Fix #148

It's two things:

1. The verbose is really poor. The user can't know if the problem is the password or if he's locked, disabled... It will be necessary modify oauth2-php.
2. The constructor has a non-default argument rightmost default one. I try to fix this with the commit f2761ae306959b87551c29fb3c30710cce255cc6 [(at this branch)](https://github.com/BraisGabin/FOSOAuthServerBundle/tree/refactor) but I have an error and I don't know how to fix it:

> Catchable Fatal Error: Argument 5 passed to FOS\OAuthServerBundle\Storage\OAuthStorage::__construct() must implement interface Symfony\Component\Security\Core\User\UserCheckerInterface, instance of FOS\UserBundle\Doctrine\UserManager given, called in [...]/app/cache/dev/appDevDebugProjectContainer.php on line 1254 and defined in [...]/vendor/friendsofsymfony/oauth-server-bundle/FOS/OAuthServerBundle/Storage/OAuthStorage.php line 87