Better accommodation for components with nested form controls.

I created a new control called Webform Structured Text, which is like the date control in that there are child elements of the control the '#value' of which need to be cleared as well as at the control level. That wasn't happening in function _webform_condtional_clear_element_values, as it assumes a 'flat' structure for all components except for date. A better way to do this would be to call a recursive function to do the clean-up, traversing through all element_children() (and all the 'progeny') of the element, clearing out any '#value' array elements it finds. The recursive function and function _webform_condtional_clear_element_values would then look like this:

/**
 * Helper function to recursively clear out element values.
 * @param array $element The element that needs values cleared.
 * @return None.
 */
function _webform_conditional_clear_element(&$element) {
  if (!isset($element['#type']) || $element['#type'] == 'markup') {
    //markup fields don't have user input to clear
    //markup is default
    return;
  }
  if (isset($element['#value']) && is_array($element['#value'])) {
    foreach ($element['#value'] as $key => $value) {
      $element['#value'][$key] = '';
    }
  }
  else {
    $element['#value'] = '';
  }
  foreach ( element_children($element) as $key ) {
    _webform_conditional_clear_element($element[$key]);
  }
}

/**
 * Clear the submitted values for an element
 * @param $element
 */
function _webform_condtional_clear_element_values(&$element, &$form_state) {
  _webform_conditional_clear_element($element); 
  // also must clear value in $form_state['values'] so it is not seen by other functions
  $reference_element = FALSE;
  $reference_set = FALSE;
  //loop thru array_parents to find var to reference under "values"
.
.
.

Patch attached. Would be great to get this into the next release. The only other way I thought of doing this would be to provide a hook for components to use to at least allow them to clear out their values themselves.

Shawn