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/plugins/phorum/init-config.php

@@ -0,0 +1,30 @@
+<?php
+
+/**
+ * Initializes the appropriate configuration from either a PHP file
+ * or a module configuration value
+ * @return Instance of HTMLPurifier_Config
+ */
+function phorum_htmlpurifier_get_config($default = false)
+{
+    global $PHORUM;
+    $config_exists = phorum_htmlpurifier_config_file_exists();
+    if ($default || $config_exists || !isset($PHORUM['mod_htmlpurifier']['config'])) {
+        $config = HTMLPurifier_Config::createDefault();
+        include(dirname(__FILE__) . '/config.default.php');
+        if ($config_exists) {
+            include(dirname(__FILE__) . '/config.php');
+        }
+        unset($PHORUM['mod_htmlpurifier']['config']); // unnecessary
+    } else {
+        $config = HTMLPurifier_Config::create($PHORUM['mod_htmlpurifier']['config']);
+    }
+    return $config;
+}
+
+function phorum_htmlpurifier_config_file_exists()
+{
+    return file_exists(dirname(__FILE__) . '/config.php');
+}
+
+// vim: et sw=4 sts=4