Moved lib/API to lib/Router

- renamed lib/API/API.php to lib/Router/Front.php
- updated namespaces in various file to account for namespace change

lib/Router/Queue.php

@@ -0,0 +1,16 @@
+<?php
+namespace MailPoet\Router;
+
+use MailPoet\Cron\Daemon;
+
+if(!defined('ABSPATH')) exit;
+
+class Queue {
+  const ENDPOINT = 'queue';
+  const ACTION_RUN = 'run';
+
+  static function run($data) {
+    $queue = new Daemon($data);
+    $queue->run();
+  }
+}