[RFC] Phpcrodm Support

Hi, Im currently working on the Symfony CMF, and am trying to establish a standard way to perform the various bundle / component functional tests.

@lsmith mentioned this bundle, and that he was considering the deprecation of the LiipFunctionalTestBundle and I thought it would be interesting to see if this would be a good fit as the standard CMF functional testing library. But to do so we need PHPCR-ODM support.

This PR basically introduces a factory to get the correct "FixtrureLoader" class, I have changed the original FixtureLoader to ORMFixtureLoader, the PHPCRFixtureLoader isn't there yet. I have also factored out the `Client` class from the fixture loader as it seemed to be an unrequired dependency - but I could be wrong!

So this is just a "what do you think" PR, it might work, but I havn't tested it, and its certainly incomplete.