Optimize predicates by prefetching roles

[SebCorbin]

There's a lot of queries around predicates, e.g.

SELECT "partnership_partnershipentitymanager"."id",        "partnership_partnershipentitymanager"."person_id",        "partnership_partnershipentitymanager"."entity_id",        "partnership_partnershipentitymanager"."with_child",        "partnership_partnershipentitymanager"."scopes"   FROM "partnership_partnershipentitymanager"  WHERE "partnership_partnershipentitymanager"."person_id" = X

These are run each a predicate is accessed, it could be prevented by using `prefetch_related_objects()' on the person if the related_name of PartnershipEntityManager.person was specified.