Reorganized new API + added legacy API support + new API

- Updated Settings Router to new standards
- Updated settings.html to reflect API change with better error handling
- Updated Settings API unit tests

lib/API/SendingQueue.php

@@ -1,6 +1,6 @@
 <?php
-namespace MailPoet\API;
-
+namespace MailPoet\API
+    ;
 
 use MailPoet\Mailer\Mailer;
 use MailPoet\Models\Newsletter;