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/RetrieveQRCode.php

@@ -37,5 +37,5 @@ ResultPrinter::printResult("Retrieved QR Code for Invoice", "Invoice", $invoice-
 // In PHP, there are many ways to present an images.
 // One of the ways, you could directly inject the base64-encoded string
 // with proper image information in front of it.
-echo '<img src="data:image/png;base64,'. $image->getImageBase64() . '" alt="Invoice QR Code" />';
+echo '<img src="data:image/png;base64,'. $image->getImage() . '" alt="Invoice QR Code" />';