Add website to client repository

Closes #1567

The main reason I'm not simply merging Annika's PR is because this
way makes it clearer that I'm taking responsibility for all this
code, that it's mostly code I wrote, and also because it makes it
easier to ensure that none of the files have been changed.

(Not that I don't personally trust Annika, but I have something
resembling an obligation to users not to expose them to risks based
on personal trust.)

website/lib/htmlpurifier/HTMLPurifier/ConfigSchema/Interchange.php

@@ -0,0 +1,42 @@
+<?php
+
+/**
+ * Generic schema interchange format that can be converted to a runtime
+ * representation (HTMLPurifier_ConfigSchema) or HTML documentation. Members
+ * are completely validated.
+ */
+class HTMLPurifier_ConfigSchema_Interchange
+{
+
+    /**
+     * Name of the application this schema is describing.
+     */
+    public $name;
+
+    /**
+     * Array of Directive ID => array(directive info)
+     */
+    public $directives = array();
+
+    /**
+     * Adds a directive array to $directives
+     */
+    public function addDirective($directive) {
+        if (isset($this->directives[$i = $directive->id->toString()])) {
+            throw new HTMLPurifier_ConfigSchema_Exception("Cannot redefine directive '$i'");
+        }
+        $this->directives[$i] = $directive;
+    }
+
+    /**
+     * Convenience function to perform standard validation. Throws exception
+     * on failed validation.
+     */
+    public function validate() {
+        $validator = new HTMLPurifier_ConfigSchema_Validator();
+        return $validator->validate($this);
+    }
+
+}
+
+// vim: et sw=4 sts=4