Mavlink File Transfer Protocol (FTP)

Changed FTP to tree view

Also added selection from tree view for downloading

FGFS multicopter HIL

Mavlink FTP: List and Download commands working end to end

Google Maps fix

Fixes to botched Qwt 6.1 update

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

Update Qwt to 6.1

Fix linux release build warning

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

Qt5 fixes

Mavlink FTP implementation List command

I was unsure how to update the QwtPlotPrintFilter code, so I just commented it out with a FIXME.

We also document how we got the source code and keep our modifications out of the Qwt directory.