Added API/Endpoint abstract class

- (re)Added Endpoints folder to both API and Router
- fixed syntax in namespaces
- xhr.responseJSON is returned to the fail()
- fixed Router endpoints (view in browser, cron,...)

lib/API/Endpoints/Cron.php

@@ -0,0 +1,36 @@
+<?php
+namespace MailPoet\API\Endpoints;
+
+use MailPoet\Cron\CronHelper;
+use MailPoet\Cron\Supervisor;
+use MailPoet\Models\Setting;
+
+if(!defined('ABSPATH')) exit;
+
+class Cron {
+  function start() {
+    $supervisor = new Supervisor($force_run = true);
+    return $supervisor->checkDaemon();
+  }
+
+  function stop() {
+    $daemon = CronHelper::getDaemon();
+    if(!$daemon || $daemon['status'] !== 'started') {
+      $result = false;
+    } else {
+      $daemon['status'] = 'stopping';
+      $result = CronHelper::saveDaemon($daemon);
+    }
+    return array(
+      'result' => $result
+    );
+  }
+
+  function getStatus() {
+    $daemon = Setting::where('name', 'cron_daemon')
+      ->findOne();
+    return ($daemon) ?
+      unserialize($daemon->value) :
+      false;
+  }
+}