I finished the multi-label support (also for other functions, which allows multiple requests in one call)

Sadly I cannot test everything, so I would love to get some feedback about those:

• * Thermo-Test user works
• * createShipment still works
• * createShipment works with multiple elements
• * createShipment shows multiple labels in Response
• * createShipment works with "ExportDocument"
• * createShipment shows the "ExportDocument" in Response
• createShipment works with "COD (Cash on delivery)"
• createShipment shows the "COD (Cash on delivery)" label in response
• * doManifest still works
• * doManifest works with multiple elements
• * doManifest shows result(s) in Response
• * deleteShipment still works
• * deleteShipment works with multiple elements
• * deleteShipment shows the result(s) in Response
• * getShipmentLabel still works
• * getShipmentLabel works with multiple elements
• * getShipmentLabel shows the result(s) in Response
• * getExportDoc still works
• * getExportDoc works with multiple elements
• * getExportDoc shows the result(s) in Response
• * validateShipment still works
• * validateShipment works with multiple elements
• * validateShipment shows the result(s) in Response

Just use the "multi-label" Branch for testing my changes.

I made some bigger changes, so I want to ensure everything works, before merging. I will merge, when every * element is tested