refactored object creation.

added more exception classes.
working on request and response classes.

framework/base/BadConfigException.php

@@ -0,0 +1,21 @@
+<?php
+/**
+ * BadConfigException class file.
+ *
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright &copy; 2008-2012 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yii\base;
+
+/**
+ * BadConfigException represents an exception caused by incorrect object configuration.
+ *
+ * @author Qiang Xue <qiang.xue@gmail.com>
+ * @since 2.0
+ */
+class BadConfigException extends \Exception
+{
+}
+