title: Prevent selection change in NSOutlineView when NSActionCell clicked
body: <p>I have a custom NSActionCell used to render some parts of some of the rows in my NSOutlineView. I can receive and respond to clicks on the NSActionCell, but the selection also changes when that cell is clicked. I'd like to prevent the selection from changing if one of my custom NSActionCells are clicked.</p>
  
  <p>Is there an easy way to do this?</p>