title: Entity relations not recognized in traits used by entity class
body: <p>If I have an entity class that uses a trait which declares entity relations, those entity relations will be ignored by the <code>php app/console doctrine:migrations:diff</code> command.</p>
  
  <p>I assume it is the same with the Symfony command <code>php app/console doctrine:schema:update --force</code>.</p>
  
  <p>For example:</p>
  
  <pre><code>trait FooTrait {
  
      /**
       * @ORM\OneToOne(targetEntity="AnotherEntity")
       * @ORM\JoinColumn(name="fk_another")
       *
       * @var AnotherEntity
       */
      private $another;
  }
  
  /**
   * @ORM\Entity
   */
  public class Bar {
  
      use FooTrait;
  
      /**
       * @var string     *
       * @ORM\Column(type="string")
       */
      private $name;
  
  }
  </code></pre>
  
  <p>Will generate a migration that creates field fk_another as <code>VARCHAR(255)</code> without any indices.</p>