Improvements and fixes

• Volume is now calculated based on length, width, and height when using the SubmitShipment command to Shipment Server.
• Added support for looking up cities in Belgium, the Netherlands, and Germany based on postcode.
• Export files are now locked until they have been fully written.
• Improved label error messages.
• Fixed issue where DG office integration prevents customers from using carriers that do not have DG goods types.
• Fixed problems with PNG output on DHL NL.
• Performance and stability improvements.
• Various technical fixes and refactoring.