Modified to use new FILE_TRANSFER_PROTOCOL message

- Also corrected system/component id usage
- Switched to new Qt5 connect api
Better debugging for Windows failure
Make sure hdr.size is always set

Otherwise we can end up generating strange CRCs.
Had to give up on bitfields
Merge pull request #849 from DonLakeFlyer/FTP

Modified to use new FILE_TRANSFER_PROTOCOL message