title: Sort over ManyToOne Relationship with KnpPaginatorBundle in Symfony2
body: <p>I'm using KnpPaginatorBundle in a Symfony2 Project. I got 2 Entities with a manyToOne Relationship.</p>
  
  <pre><code>/**
   * @ORM\Entity
   * @ORM\Table(name="foo")
   */
  class foo {
     ...
  
     /**
       * @ORM\ManyToOne(targetEntity="abc\DemoBundle\Entity\Bar")
       * @ORM\JoinColumn(name="bar_id", referencedColumnName="id")
       */
      protected $bar;
  
      ...
  }
  
  /**
   * @ORM\Entity
   * @ORM\Table(name="bar")
   */
  class Bar {
     ...
  
      /**
       * @ORM\Column(type="string", length=50, nullable=true)
       */
      protected $name;
  
      ...
  }
  </code></pre>
  
  <p>Now I want to sort with the KnpPaginatorBundle </p>
  
  <pre><code>&lt;{{  entities.sortable('bar', 'i.bar')|raw }}
  </code></pre>
  
  <p>I get following error message</p>
  
  <pre><code>There is no such field [bar] in the given Query component, aliased by [i]
  </code></pre>
  
  <p>Is there any way to make bar in foo sortable using bar.name?</p>
  
  <p>Cheers</p>