Many more GUI tweaks

Changes made:
- Response print now after response collected as expected
- Byteswap performed whilst converting message to byte array
- Work done on return values and how they are funnelled through to the
main return value of the SendMessage() method
- Added scroll bar to response text box

Still to do:
- Investigate error code 10061 on tempSocket.Connect()
- Add error code enums to prevent return values appearing as magic
numbers
- Complete "Connection" tab to allow the user to enter an IP address to
connect to (use C# settings file and pass setting to SendMessage()
method)
- Develop a method to find a free port automatically so that the user
only has to enter the IP