title: Yii CgridView: Sorting or filtering removes my "custom" filter
body: <p><strong>Situation:</strong>
  I created a kind of wizard with a CGridView at the bottom. Every time the user selects something in the wizard, the grid will be "filtered" (without AJAX) by the model its search function. I keep all the user his "answers" of the previous steps in hidden fields, so I can use them every step in my wizard again for filtering.</p>
  
  <p><strong>Problem:</strong>
  When I sort or filter directly in the cgridview (with the default filter fields and sorting titles), he doesn't use my hidden field values anymore. I'm probably a bit lost (I'm pretty new to YII btw). How can I give the default filter and sort requests the values of my hiddenfields, so they will be used in the search function? I can see that I need to add params like for example Person[name] to the request, but I don't know how...</p>