[3.1.0] Implement ConfigSchema interchange

- Implement exception hierarchy

git-svn-id: http://htmlpurifier.org/svnroot/htmlpurifier/trunk@1582 48356398-32a2-884e-a903-53898d9a118a

library/HTMLPurifier/ConfigSchema/Exception.php

@@ -0,0 +1,9 @@
+<?php
+
+/**
+ * Exceptions related to configuration schema
+ */
+class HTMLPurifier_ConfigSchema_Exception extends HTMLPurifier_Exception
+{
+    
+}