Update lib/Doctrine/ORM/EntityRepository.php

Add "indexby" missing parameter that permit an "index by" easily.

Ex : 
#Acme\AcmeBundle\Repository
#Before
public function findAllIndexById(){
    $qb = $this->_em->createQueryBuilder()
                              ->select('root')
                              ->from('Acme', 'root', 'root.id');
  /*...*/
}

#After
public function findAllIndexById(){
    $qb = $this->createQueryBuilder('root','root.id');
    /*...*/
}