Fix invalid "emailer_prepare" Hook

- Use IEmail instead of array data
- Introduce "composer" based library for phpmailer

phpmailer/vendor/autoload.php

@@ -0,0 +1,7 @@
+<?php
+
+// autoload.php @generated by Composer
+
+require_once __DIR__ . '/composer/autoload_real.php';
+
+return ComposerAutoloaderInitPhpMailerAddon::getLoader();