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/Proprietary.php

@@ -0,0 +1,40 @@
+<?php
+
+/**
+ * Module defines proprietary tags and attributes in HTML.
+ * @warning If this module is enabled, standards-compliance is off!
+ */
+class HTMLPurifier_HTMLModule_Proprietary extends HTMLPurifier_HTMLModule
+{
+    /**
+     * @type string
+     */
+    public $name = 'Proprietary';
+
+    /**
+     * @param HTMLPurifier_Config $config
+     */
+    public function setup($config)
+    {
+        $this->addElement(
+            'marquee',
+            'Inline',
+            'Flow',
+            'Common',
+            array(
+                'direction' => 'Enum#left,right,up,down',
+                'behavior' => 'Enum#alternate',
+                'width' => 'Length',
+                'height' => 'Length',
+                'scrolldelay' => 'Number',
+                'scrollamount' => 'Number',
+                'loop' => 'Number',
+                'bgcolor' => 'Color',
+                'hspace' => 'Pixels',
+                'vspace' => 'Pixels',
+            )
+        );
+    }
+}
+
+// vim: et sw=4 sts=4