WIP - Using Symfony Propel Bridge as main type guesser

I've moved all config file to XML and addedd guessers to be compliant with the main implementation.

@rande Can we consider using Symfony\Component\Form\FormTypeGuesserInterface instead of Sonata\AdminBundle\Model\ModelManagerInterface\TypeGuesserInterface in SonataAdminBundle ? I think the current interface is not compliant with the Active Record pattern used in Propel. I will do a PR on SonataDoctrineORMAdminBundle if you agree.