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/Strategy/Composite.php

@@ -0,0 +1,30 @@
+<?php
+
+/**
+ * Composite strategy that runs multiple strategies on tokens.
+ */
+abstract class HTMLPurifier_Strategy_Composite extends HTMLPurifier_Strategy
+{
+
+    /**
+     * List of strategies to run tokens through.
+     * @type HTMLPurifier_Strategy[]
+     */
+    protected $strategies = array();
+
+    /**
+     * @param HTMLPurifier_Token[] $tokens
+     * @param HTMLPurifier_Config $config
+     * @param HTMLPurifier_Context $context
+     * @return HTMLPurifier_Token[]
+     */
+    public function execute($tokens, $config, $context)
+    {
+        foreach ($this->strategies as $strategy) {
+            $tokens = $strategy->execute($tokens, $config, $context);
+        }
+        return $tokens;
+    }
+}
+
+// vim: et sw=4 sts=4