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/AttrDef/HTML/Bool.php

@@ -0,0 +1,48 @@
+<?php
+
+/**
+ * Validates a boolean attribute
+ */
+class HTMLPurifier_AttrDef_HTML_Bool extends HTMLPurifier_AttrDef
+{
+
+    /**
+     * @type bool
+     */
+    protected $name;
+
+    /**
+     * @type bool
+     */
+    public $minimized = true;
+
+    /**
+     * @param bool $name
+     */
+    public function __construct($name = false)
+    {
+        $this->name = $name;
+    }
+
+    /**
+     * @param string $string
+     * @param HTMLPurifier_Config $config
+     * @param HTMLPurifier_Context $context
+     * @return bool|string
+     */
+    public function validate($string, $config, $context)
+    {
+        return $this->name;
+    }
+
+    /**
+     * @param string $string Name of attribute
+     * @return HTMLPurifier_AttrDef_HTML_Bool
+     */
+    public function make($string)
+    {
+        return new HTMLPurifier_AttrDef_HTML_Bool($string);
+    }
+}
+
+// vim: et sw=4 sts=4