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/AttrTransform/Length.php

@@ -0,0 +1,45 @@
+<?php
+
+/**
+ * Class for handling width/height length attribute transformations to CSS
+ */
+class HTMLPurifier_AttrTransform_Length extends HTMLPurifier_AttrTransform
+{
+
+    /**
+     * @type string
+     */
+    protected $name;
+
+    /**
+     * @type string
+     */
+    protected $cssName;
+
+    public function __construct($name, $css_name = null)
+    {
+        $this->name = $name;
+        $this->cssName = $css_name ? $css_name : $name;
+    }
+
+    /**
+     * @param array $attr
+     * @param HTMLPurifier_Config $config
+     * @param HTMLPurifier_Context $context
+     * @return array
+     */
+    public function transform($attr, $config, $context)
+    {
+        if (!isset($attr[$this->name])) {
+            return $attr;
+        }
+        $length = $this->confiscateAttr($attr, $this->name);
+        if (ctype_digit($length)) {
+            $length .= 'px';
+        }
+        $this->prependCSS($attr, $this->cssName . ":$length;");
+        return $attr;
+    }
+}
+
+// vim: et sw=4 sts=4