More Vault API Samples

- Updated Samples for Vault APIs
- Updated Payment Execute to be more verbose
- Delete Plan Sample Update
- Fixes #168

sample/vault/GetCreditCard.php

@@ -8,6 +8,7 @@
 // the process of retrieving a saved CreditCard
 /** @var CreditCard $card */
 $card = require 'CreateCreditCard.php';
+$id = $card->getId();
 
 use PayPal\Api\CreditCard;