title: How to add a dropdown to CK Editor with a list of class names
body: <p>How to add a dropdown to CK Editor with a list of class names that I can then assign to text? 
  I need to add some classes for images too and I believe the definition needs to be set for each tag type.
  I've studied the docs and there's examples for inline styling but I need classes.</p>
  
  <p>In fact this is for CK Editor used within Sonata CMS, but it must be the same structure.</p>
  
  <p>Weird that it's not there - TinyMce can do it easily.</p>