- Download working again
- Fixed lots of bad error handling

writeFileAccumulator contents cleared on errors, nack or ack timeout
memcpy used to transfer data to request message buffer

Plus a large number of other changes to allow for orderly shutdown of
objects without crashes or asserts. This is need for unit tests to
create/delete global state around every test.

Otherwise we can end up generating strange CRCs.

- Also corrected system/component id usage
- Switched to new Qt5 connect api

Also restructured signals to be more command-centric as opposed to
ui-centric.

Added:
- sequence numbers
- better filtering for image encapsulated data messages versus FTP
- directory list now contains file sizes
- open command now returns file size in data

Also added selection from tree view for downloading

Also modified protocol to better support eof’s on list and read
commands.

Also changes for Ack timeouts and unit testing