title: ManyToMany relation don't create all tables
body: <p>I have two simple entities. One is for services, and one that contains products. Many services can have many products.</p>
  
  <p>For example, service1 is composed from product2 and product6, service2 is composed from product1 and product2, ...</p>
  
  <p>I've created the products entity (id and name), and then created the service entity with id, name and:</p>
  
  <pre><code> /**
     * @var ArrayCollection
     *
     * @ORM\ManyToMany(targetEntity="Product", cascade={"persist", "remove"}, mappedBy="service")
     */
     private $products;
  </code></pre>
  
  <p>But this only generate two real tables, one called service and one called product. And service table even don't have a field called products.</p>
  
  <p>I think that this must create another table called service_product to store the relationship between the two tables.</p>
  
  <p>What's wrong ?</p>