Filter API is not unified between ODM and ORM

Hi,

I'm implementing some functionality around filters which will ideally work for both ORM and ODM. The API for managing filters is different on `Doctrine\ORM\EntityManager` and `Doctrine\ODM\MongoDB\DocumentManager`, while the CouchDB implementation of ODM has no filter concept.

For example, ORM EntityManager has getFilters(), hasFilters(), while ODM MongoDB DocumentManager has getFilterCollection().

I was wondering what your thoughts were on defining the filter API in an interface, to improve consistency when implementing cross-library functionality?

Thanks,
Craig