Two hooks for DoctrineBundle to allow ContainerFilterCollection

Allows the DoctrineBundle to inject a ```ContainerFilterCollection``` that creates filters through dependency injection. See doctrine/DoctrineBundle#245.

Would prefer to inject the ```FilterCollection``` into the constructor of the em, but since they have a cyclic dependency I chose setter injection.
This is a bit messy imo. The filter factory has a dependency to configuration, and configuration has a dependency to filter factory?