title: angularJS filter expression in ng-repeat
body: <p>I would like to know what is the most elegant and simple way to implement this.
  I need to add a filter expression for a ng-repeat that would filter 2 conditions from one property.</p>
  
  <p>In this example <a href="http://plnkr.co/edit/OMQxXvSjtuudMRGE4eZ8?p=preview" rel="noreferrer">http://plnkr.co/edit/OMQxXvSjtuudMRGE4eZ8?p=preview</a> </p>
  
  <ul>
  <li>If you enter A, it would display checkbox for A, </li>
  <li>enter B - display checkbox for B.</li>
  </ul>
  
  <p>But I want to display the specified checkboxes plus anything with empty condition. 
  There is no condition for C, so:</p>
  
  <ul>
  <li>if you enter A, I want to display both A and C checkboxes, </li>
  <li>enter B, I want to display both B and C checkboxes.</li>
  </ul>