title: Many To Many Mapping Issue
body: <p>I'm currently trying to map music related data using Doctrine2's POPO Annotations.</p>
  
  <p>I haven't had problems mapping any other many-to-many relations, but one specific relation is giving me trouble. It does not throw an error, but the mapping does not get inserted into the mapping table (<code>artist_album</code>)</p>
  
  <p><strong>Artist</strong>:</p>
  
  <pre><code>&lt;?php
  /**
   * @orm:Entity
   * @orm:Table(name="artist")
   */
  class Artist
  {
  
      ...
  
       /**
       * @orm:ManyToMany(targetEntity="Company\MusicBundle\Entity\Album", inversedBy="artists", cascade={"persist"})
       * @orm:JoinTable(name="artist_album",
       *      joinColumns={@orm:JoinColumn(name="artist_id", referencedColumnName="id")},
       *      inverseJoinColumns={@orm:JoinColumn(name="album_id", referencedColumnName="id")})
       *      
       * @var ArrayCollection
       */
      private $albums;
  
      ...
  
  }
  </code></pre>
  
  <p><strong>Album</strong>
      
  
  <pre><code>    ....
  
      /**
       * @orm:ManyToMany(targetEntity="Company\MusicBundle\Entity\Artist", mappedBy="albums", cascade={"persist"})
       * 
       * @var ArrayCollection
       */
      private $artists;
  
      ...
  
  }
  </code></pre>
  
  <p>I'm sure it's just something in I've done wrong in the mapping, but I just can't put my proverbial finger on it.</p>