1) entity, collection, composite, any fetches are created and pushed by startingAttribute() (pushed if they are IMMEDIATE/JOIN)
2) they are popped by finishingAttribute()
3) only the root EntityReturn/Collection return is pushed by startingEntity()/startingCollection() (this is unchanged)
4) only the root EntityReturn/Collection return is popped by finishingEntity()/finishingCollection()
5) AttributeFetch is added to specify a particular Fetch is a real attribute; EntityFetchImpl, CollectionFetchImpl, AnyFetchImpl will be renamed to EntityAttributeFetchImpl, CollectionAttributeFetchImpl, AnyAttributeFetchImpl and will implement AttributeFetch; CompositeAttributeFetchImpl will be added