avoid reloading translated fields when not needed

this avoids unnecessary reloads when https://github.com/doctrine/phpcr-odm/blob/master/lib/Doctrine/ODM/PHPCR/UnitOfWork.php#L528 triggers because of language fallback. imo it makes sense in general because loadTranslation should not be abused to refresh a document.

while investigating, found some issues around refreshing and cleaned those up too.