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/composer/autoload_real.php

@@ -47,6 +47,24 @@ class ComposerAutoloaderInitFriendica
 
         $loader->register(true);
 
+        if ($useStaticLoader) {
+            $includeFiles = Composer\Autoload\ComposerStaticInitFriendica::$files;
+        } else {
+            $includeFiles = require __DIR__ . '/autoload_files.php';
+        }
+        foreach ($includeFiles as $fileIdentifier => $file) {
+            composerRequireFriendica($fileIdentifier, $file);
+        }
+
         return $loader;
     }
 }
+
+function composerRequireFriendica($fileIdentifier, $file)
+{
+    if (empty($GLOBALS['__composer_autoload_files'][$fileIdentifier])) {
+        require $file;
+
+        $GLOBALS['__composer_autoload_files'][$fileIdentifier] = true;
+    }
+}