Also added selection from tree view for downloading

Mavlink FTP: List and Download commands working end to end

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

Plotting data now defaults to drawing a line with no symbols.

Qt5 fixes

Mavlink FTP implementation List command

These changes prevent random encapsulated data packets as being thought
to be images.

Also changes for Ack timeouts and unit testing

Also deleted invalid line drawing options.

espeak: provide string length including 0 character