title: Have ReSharper keep 'using System;' when optimizing usings
body: <p>I was wondering if there is some option to keep ReSharper from removing just the <code>using System;</code> directive? Perhaps this is configurable somewhere?</p>
  
  <p>Also, is there a way to have ReSharper sort the remaining directives just as Visual Studio 2008 does it (alphabetically, I think)?</p>
  
  <p>Thanks.</p>