title: QGroupBox title vertical alignment
body: <p>I have QGroupBox in my UI. The basic style is 2px width border, border radius and the title being vertically centered.</p>
  
  <p>I used the following style to my stylesheet (which is in a .qrc, applied in the main using app->setStylesheet):</p>
  
  <pre><code>QGroupBox {
      border: 1px solid #22a4bc;
      border-radius: 0px;
  }
  
  QGroupBox::title {
      subcontrol-origin: margin;
      subcontrol-position: top; /* position at the top center */
  }
  </code></pre>
  
  <p>The problem is, the title is now a few pixel down, and actually over the element IN the groupbox. </p>
  
  <p>I want to set it centered. I tried vertical-align, subcontrol-align, subcontrol-alignment, even top: -5px which actually centers the title, but trim the text that is higher than the border.
  I didn't find any answer here on SO or on the Qt forum that resolve my problem.</p>
  
  <p>Does anybody know how to set the title's vertical alignment to back center?
  (I use C++, Qt 5.2.1 / msvc2012, Qt Creator 3.6.1 / Windows 7)</p>