title: valid constraint does not support group options in symfony2
body: <p>I need to cascade validation in symfony2 form unless for specified group. </p>
  
  <p>here symfony team told that group option is not supported in Valid constraint
  <a href="https://github.com/symfony/symfony/issues/4893" rel="nofollow">https://github.com/symfony/symfony/issues/4893</a></p>
  
  <p>How to do it ?</p>
  
  <p>Details:</p>
  
  <p>I have a User Entity has address property which is a foreign key to Address Entity. Also i have Entity called business having User as property and also Address property. I need to validate address for User but, without validating it When User is a property of Business...</p>
  
  <p>Schema</p>
  
  <pre><code>Class Address {
      ...
  }
  
  Class User {
       /**
       * @Assert\Valid(groups={"user"})
       */
       private $address;
  }
  
  Class Business {
      /**
       * @Assert\Valid(groups={"business"})
       */
       private $user;
      /**
       * @Assert\Valid(groups={"business"})
       */
       private $address;
  }
  </code></pre>
  
  <p>So I need to validate The address inside User only for User Forms but not for Business.</p>
  
  <p>Thank you</p>