Enabled Vault Credit Card List API

- Added Credit Card List API Operation
- Updated Credit Card to include new properties
- Updated Tests
- Updated Samples
- Fixed Billing Agreement Sample (Expired Set Date).

tests/PayPal/Test/Functional/resources/BillingAgreementsFunctionalTest/testCreateCCAgreement.json

@@ -20,7 +20,7 @@
         "body": {
             "name": "DPRP",
             "description": "Payment with credit Card ",
-            "start_date": "2015-06-17T9:45:04Z",
+            "start_date": "2019-06-17T9:45:04Z",
             "plan": {
                 "id": "P-1WJ68935LL406420PUTENA2I"
             },

tests/PayPal/Test/Functional/resources/BillingAgreementsFunctionalTest/testCreatePayPalAgreement.json

@@ -20,7 +20,7 @@
         "body": {
             "name": "Base Agreement",
             "description": "Basic agreement",
-            "start_date": "2015-06-17T9:45:04Z",
+            "start_date": "2019-06-17T9:45:04Z",
             "plan": {
                 "id": "P-1WJ68935LL406420PUTENA2I"
             },