adding docs for Query::reset() method

lib/Doctrine/Query.php

@@ -119,6 +119,10 @@ class Doctrine_Query extends Doctrine_Query_Abstract implements Countable
     {
         return new Doctrine_Query($conn);
     }
+
+    /**
+     * Resets the query object, so that it can be used again for a fresh query
+     */
     public function reset()
     {
         $this->_pendingJoinConditions = array();