Adds MP API facade

lib/API/MP/API.php

@@ -0,0 +1,15 @@
+<?php
+namespace MailPoet\MP\API;
+
+if(!defined('ABSPATH')) exit;
+
+class API {
+  static function __callStatic($version, $arguments) {
+    $api_class = sprintf('%s\%s\API', __NAMESPACE__, $version);
+    if(class_exists($api_class)) {
+      $api = new $api_class();
+      return $api;
+    }
+    throw new \Exception(__('Invalid API version.', 'mailpoet'));
+  }
+}

lib/API/MP/v1/API.php

@@ -0,0 +1,7 @@
+<?php
+namespace MailPoet\API\MP\v1;
+
+if(!defined('ABSPATH')) exit;
+
+class API {
+}