title: Add 2 UILabels in UINavigationBar titleView on top of one another
body: <p>I have a custom <code>UINavigationBar</code> with a 2 line label in its <code>titleView</code>:</p>
  
  <pre><code>        UILabel *navBarLabel = [[UILabel alloc] initWithFrame:CGRectZero];  
          UINavigationItem *item = [[UINavigationItem alloc] init];  
          navBarLabel.backgroundColor = [UIColor clearColor];
          navBarLabel.font = [UIFont fontWithName:@"HelveticaNeue" size:14];
          navBarLabel.numberOfLines = 2;
          navBarLabel.textAlignment = UITextAlignmentCenter;
          navBarLabel.textColor = [UIColor colorWithRed:124.0/255.f green:125.0/255.f blue:128.0/255.f alpha:1.0];
          navBarLabel.text = @"This\nis an example";
          [navBarLabel sizeToFit];
          item.titleView = navBarLabel;
  </code></pre>
  
  <p>But instead of making my <code>UILabel</code> with 2 lines of texts, I would like to add 2 <code>UILabels</code>, <em>one on top of another</em> to achieve the customisation of the font in each of the 'lines' separately. How is it implemented? Any ideas?</p>