title: Overriding keyDown: in an NSTableView category disables arrow key handling
body: <p>I have an <code>NSTableView</code> and I have some issues with its default behavior.</p>
  
  <p>If I've overridden the <code>keyDown:</code> method in a category as follows:</p>
  
  <pre><code>- (void) keyDown:(NSEvent *)event {
      [super keyDown:event];
  }
  </code></pre>
  
  <p>I can't change the row selection with the keyboard arrow keys anymore. Why is that? </p>