Enabled Billing Plans and Agreements APIs

- Added API Classes, Samples, and Tests
- Updated Functional Tests
- Updated Documentation with new SDK Name
- Updated Few Samples to use newer nicer result page

sample/billing/UpdateBillingAgreement.php

@@ -0,0 +1,47 @@
+<?php
+
+// # Update an agreement
+//
+// This sample code demonstrate how you can update a billing agreement, as documented here at:
+// https://developer.paypal.com/webapps/developer/docs/api/#update-an-agreement
+// API used: /v1/payments/billing-agreements/<Agreement-Id>
+
+// Retrieving the Agreement object from Create Agreement Sample to demonstrate the List
+/** @var Agreement $createdAgreement */
+$createdAgreement = require 'CreateBillingAgreementWithCreditCard.php';
+
+use PayPal\Api\Agreement;
+use PayPal\Api\PatchRequest;
+use PayPal\Api\Patch;
+
+$patch = new Patch();
+
+$patch->setOp('replace')
+    ->setPath('/')
+    ->setValue(json_decode('{
+            "description": "New Description",
+            "shipping_address": {
+                "line1": "2065 Hamilton Ave",
+                "city": "San Jose",
+                "state": "CA",
+                "postal_code": "95125",
+                "country_code": "US"
+            }
+        }'));
+$patchRequest = new PatchRequest();
+$patchRequest->addPatch($patch);
+try {
+    $createdAgreement->update($patchRequest, $apiContext);
+
+    // Lets get the updated Agreement Object
+    $agreement = Agreement::get($createdAgreement->getId(), $apiContext);
+
+} catch (PayPal\Exception\PPConnectionException $ex) {
+    echo "Exception: " . $ex->getMessage() . PHP_EOL;
+    var_dump($ex->getData());
+    exit(1);
+}
+
+ResultPrinter::printResult("Updated the Agreement with new Description and Updated Shipping Address", "Agreement", $agreement->getId(), $patchRequest, $agreement);
+
+return $agreement;