Replace existing autoloader with Composer-supplied

- Move Friendica namespace to `src`
- Move required `ezyang/htmlpurifier` to vendor
- Remove existing static autoloader
- Change boot.php reference to the autoloader

vendor/ezyang/htmlpurifier/library/HTMLPurifier/HTMLModule/Iframe.php

@@ -0,0 +1,51 @@
+<?php
+
+/**
+ * XHTML 1.1 Iframe Module provides inline frames.
+ *
+ * @note This module is not considered safe unless an Iframe
+ * whitelisting mechanism is specified.  Currently, the only
+ * such mechanism is %URL.SafeIframeRegexp
+ */
+class HTMLPurifier_HTMLModule_Iframe extends HTMLPurifier_HTMLModule
+{
+
+    /**
+     * @type string
+     */
+    public $name = 'Iframe';
+
+    /**
+     * @type bool
+     */
+    public $safe = false;
+
+    /**
+     * @param HTMLPurifier_Config $config
+     */
+    public function setup($config)
+    {
+        if ($config->get('HTML.SafeIframe')) {
+            $this->safe = true;
+        }
+        $this->addElement(
+            'iframe',
+            'Inline',
+            'Flow',
+            'Common',
+            array(
+                'src' => 'URI#embedded',
+                'width' => 'Length',
+                'height' => 'Length',
+                'name' => 'ID',
+                'scrolling' => 'Enum#yes,no,auto',
+                'frameborder' => 'Enum#0,1',
+                'longdesc' => 'URI',
+                'marginheight' => 'Pixels',
+                'marginwidth' => 'Pixels',
+            )
+        );
+    }
+}
+
+// vim: et sw=4 sts=4