title: propel pseudo column sorting
body: <p>Basically I want to make a pseudo column by which I'll sort. This is my SQL Query </p>
  
  <pre><code>SELECT I.*, ((I.width*175)/I.height) as relativeWidth
  FROM Image I
  order by relativeWidth asc
  </code></pre>
  
  <p>How can I do it in propel without writing direct SQL ? and I don't want to make a view and query it.</p>