Updated Samples
First Update on Invoicing APIs
More Invoice API Updates
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
Removed Mandate on CorelationId from Future Payment

- Removed backward compatibility on headers.
- Only sends 'Paypal-Application-Correlation-Id' instead of 'PAYPAL-CLIENT-METADATA-ID'