ODM support? WebTestCase::cleanDatabase requires ORM\EntityManager

Official documentation says it is possible to use mongodb as connection
`$this->loadFixtures($fixtures, null, 'doctrine_mongodb');`
but when tried we see:
`Liip\FunctionalTestBundle\Test\WebTestCase::cleanDatabase() must be an instance of Doctrine\ORM\EntityManager, instance of Doctrine\ODM\MongoDB\DocumentManager given`

`Liip\FunctionalTestBundle\Test\WebTestCase::cleanDatabase` requires
Doctrine\ORM\EntityManager (Hardcoded dependency to ORM) not
Doctrine\Common\Persistence\ObjectManager interface

https://github.com/liip/LiipFunctionalTestBundle/blob/master/Test/WebTestCase.php#L476

Start at Test/WebTestCase.php around line 476 and trace cleanDatabase() from loadFixtures(..., 'doctrine_mongodb'); inspect how the EntityManager type requirement is applied. Done means the documented MongoDB fixture path no longer fails because it receives a Doctrine ODM DocumentManager instead of an ORM EntityManager.

Written by the indexing model from the issue text.