title: How to update the columnDef of an angular ui-grid column dynamically
body: <p>So the issue I'm facing is I would like to update the <code>field</code> property of a <code>columnDef</code> definition to show a different value based on some configuration that's being passed into the directive.  I have a dumbed down version in this plunk:</p>
  
  <p><a href="http://plnkr.co/edit/gmjUcQsnIOpqWwkoYiI8?p=preview" rel="nofollow">http://plnkr.co/edit/gmjUcQsnIOpqWwkoYiI8?p=preview</a></p>
  
  <p>Clicking the button in that plunk should switch the emails from <code>actual</code> to <code>pretend</code>.  It's looping over the <code>columnDefs</code> on scope and then altering the field to be <code>email.pretend</code> from <code>email.actual</code>.  Do I need some kind of "refresh" function after changing the columnDefs?  I tried <code>gridApi.core.refresh()</code> but that did not do anything.  Thanks for any input!</p>