Samples for All Invoice Operations including QR Code

- Invoice search method is static now
- Shipping Info has proper Phone Params
- Small Changes to Image Class
- Updated Sample Docs

sample/invoice/SearchInvoices.php

@@ -0,0 +1,36 @@
+<?php
+
+// # Search Invoices Sample
+// This sample code demonstrate how you can
+// search invoices from history.
+
+/** @var Invoice $invoice */
+$invoice = require 'CreateInvoice.php';
+use PayPal\Api\Invoice;
+use PayPal\Api\Search;
+
+try {
+    // ### Search Object
+    // Fill up your search criteria for Invoice search.
+    // Using the new way to inject raw json string to constructor
+    $search = new Search(
+        '{
+          "start_invoice_date" : "2010-05-10 PST",
+          "end_invoice_date" : "2019-05-11 PST",
+          "page" : 1,
+          "page_size" : 20,
+          "total_count_required" : true
+        }'
+    );
+
+    // ### Search Invoices
+    // Retrieve the Invoice History object by calling the
+    // static `search` method on the Invoice class.
+    // Refer the method doc for valid values for keys
+    // (See bootstrap.php for more on `ApiContext`)
+    $invoices = Invoice::search($search, $apiContext);
+} catch (Exception $ex) {
+    ResultPrinter::printError("Search Invoice", "Invoice", null, null, $ex);
+    exit(1);
+}
+ResultPrinter::printResult("Search Invoice", "Invoice", null, $search, $invoices);