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/Injector/DisplayLinkURI.php

@@ -0,0 +1,26 @@
+<?php
+
+/**
+ * Injector that displays the URL of an anchor instead of linking to it, in addition to showing the text of the link.
+ */
+class HTMLPurifier_Injector_DisplayLinkURI extends HTMLPurifier_Injector
+{
+
+    public $name = 'DisplayLinkURI';
+    public $needed = array('a');
+
+    public function handleElement(&$token) {
+    }
+
+    public function handleEnd(&$token) {
+        if (isset($token->start->attr['href'])){
+            $url = $token->start->attr['href'];
+            unset($token->start->attr['href']);
+            $token = array($token, new HTMLPurifier_Token_Text(" ($url)"));
+        } else {
+            // nothing to display
+        }
+    }
+}
+
+// vim: et sw=4 sts=4