title: knockout Validation: Any option to apply the errorElementClass to parent of input?
body: <p>Does the Knockout validation plugin have any option to apply the error class to the parent or parent's-parent of the input in error?  If not can anybody suggest an approach to modify knockout validation to do this?</p>
  
  <p>Please see the following fiddle for an example of what I'm trying to achieve.  Out of the box knockout validation sets the class of the input, but I want it to instead set the class of the containing control-group:</p>
  
  <p><a href="http://jsfiddle.net/fbA4m/1/" rel="noreferrer">http://jsfiddle.net/fbA4m/1/</a></p>
  
  <p><strong>View</strong></p>
  
  <pre><code>&lt;p&gt;Clear the field and tab out of it to "see" the current behaviour - error class is added directly to the input by knockout validation. But I want to add class "error" to control-group containing the input instead of directly to the input.&lt;/p&gt;
  &lt;div class="form-horizontal"&gt;
  &lt;div class="control-group"&gt;
  &lt;label class="control-label"&gt;Field&lt;/label&gt;
  &lt;div class="controls"&gt;
  &lt;input type="text" data-bind="value: testField" class=""&gt;
  &lt;/div&gt;
  &lt;/div&gt;
      &lt;button data-bind="click: setErrorOnControlGroup"&gt;Click to see desired effect&lt;/button&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>Javascript</p>
  
  <pre><code>ko.validation.configure({
      registerExtenders: true,
      messagesOnModified: true,
      decorateElement: true,
      errorClass: 'error',
      insertMessages: false,
      parseInputAttributes: true,
      messageTemplate: null
  });
  
  var viewModel = {
      testField: ko.observable("123").extend({required: true}),
      setErrorOnControlGroup: function() {
          $("input.error").removeClass("error");
          $(".control-group").addClass("error");
      }
  };
  
  ko.applyBindings(viewModel);
  </code></pre>
  
  <p><strong>Stylesheet</strong> (Illustrative only - I shouldn't need this because I want to the use the twitter bootstrap styles)</p>
  
  <pre><code>/*NOTE: This is not actually the style I want, it just illustrates the default behaviour of knockout validation*/
  input.error {
      background-color: #aaffaa;
  }
  </code></pre>
  
  <p>I ask because I'm using twitter bootstrap styling and it uses the input's parent control-group element to style "error" inputs.</p>