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/ConfigSchema/Interchange.php

@@ -0,0 +1,47 @@
+<?php
+
+/**
+ * Generic schema interchange format that can be converted to a runtime
+ * representation (HTMLPurifier_ConfigSchema) or HTML documentation. Members
+ * are completely validated.
+ */
+class HTMLPurifier_ConfigSchema_Interchange
+{
+
+    /**
+     * Name of the application this schema is describing.
+     * @type string
+     */
+    public $name;
+
+    /**
+     * Array of Directive ID => array(directive info)
+     * @type HTMLPurifier_ConfigSchema_Interchange_Directive[]
+     */
+    public $directives = array();
+
+    /**
+     * Adds a directive array to $directives
+     * @param HTMLPurifier_ConfigSchema_Interchange_Directive $directive
+     * @throws HTMLPurifier_ConfigSchema_Exception
+     */
+    public function addDirective($directive)
+    {
+        if (isset($this->directives[$i = $directive->id->toString()])) {
+            throw new HTMLPurifier_ConfigSchema_Exception("Cannot redefine directive '$i'");
+        }
+        $this->directives[$i] = $directive;
+    }
+
+    /**
+     * Convenience function to perform standard validation. Throws exception
+     * on failed validation.
+     */
+    public function validate()
+    {
+        $validator = new HTMLPurifier_ConfigSchema_Validator();
+        return $validator->validate($this);
+    }
+}
+
+// vim: et sw=4 sts=4