Not showing when using doctrine odm with prime parameter.

Hi,
KNP paginator is great, but I have one issue with it. If I make query with prime->(true), all working except pagination links is not rendered. Here is my query:

```
$qb = $dm->createQueryBuilder('AppBundle\Document\Post');
$qb->field('forum')->references($document)
->field('author')->prime(true)
->sort('created', 'asc');
```

When I remove `->field('author')->prime(true)` it's show again, but it's not good because each author of post need separate db query.

Start by reproducing the shown Doctrine ODM query with field('author')->prime(true), then compare pagination-link rendering with and without priming. Trace the Doctrine ODM pagination and link-generation paths; done means links render while primed authors remain supported.

Written by the indexing model from the issue text.