title: ZF2 Form getData returns unvalidated data
body: <p>I just can't get my first ZF2 form to work!
  Here is the abbreviated controller action to demonstrate my workflow:</p>
  
  <pre><code>$viewData['form'] = $form = new InstituteEditForm();
  $form-&gt;setInputFilter(new InstituteInputFilter());
  $defaultValues = ...;
  $form-&gt;populateValues($defaultValues);
  if ($request-&gt;isPost()) {
      $form-&gt;setData($request-&gt;getPost());
      if ($form-&gt;isValid()) {
          print_r('VALID&lt;br/&gt;');
          var_dump($form-&gt;getData());
      } else {
          print_r('INVALID&lt;br/&gt;');
          var_dump($form-&gt;getMessages());
          var_dump($form-&gt;getData());
      }
  }
  return new ViewModel($viewData);
  </code></pre>
  
  <p>The InstituteInputFilter defines Inputs with Filters and Validators for <strong>some</strong> elements, but not for all.
  The problem is, that in case the form validates fine, form->getData() returns <strong>all</strong> values, not just those that have an Input attached, i.e. <strong>it returns unvalidated data</strong>. This should not be the case, should it?</p>
  
  <p>Thank you so much!</p>