title: Why, in Model.full_clean, is clean_fields called before clean?
body: <p>Is there a reason, in <code>Model.full_clean</code>, for <code>clean_fields</code> be called before <code>clean</code>?
  In my project, it would be more reasonable if I could first do my validations to then validate <code>clean_fields</code> stuff, like in this situation:</p>
  
  <pre><code>class MyModel(models.Model):
      status = models.IntegerField(blank=False, null=False)
  
      def clean(self):
          if not self.status:
              self.status = 0
  </code></pre>
  
  <p>Would be any problem changing this ordering in <code>full_clean</code>?</p>