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.func.php

@@ -0,0 +1,23 @@
+<?php
+
+/**
+ * @file
+ * Defines a function wrapper for HTML Purifier for quick use.
+ * @note ''HTMLPurifier()'' is NOT the same as ''new HTMLPurifier()''
+ */
+
+/**
+ * Purify HTML.
+ * @param $html String HTML to purify
+ * @param $config Configuration to use, can be any value accepted by
+ *        HTMLPurifier_Config::create()
+ */
+function HTMLPurifier($html, $config = null) {
+    static $purifier = false;
+    if (!$purifier) {
+        $purifier = new HTMLPurifier();
+    }
+    return $purifier->purify($html, $config);
+}
+
+// vim: et sw=4 sts=4