Fix Mav2 handshake

FlightDisplayViewWidgets: increase the maximum widget size from 200 to 400

Fix joystick tx mode initialization

Update MissionController.cc

Still does not support multi-vehicle

On large/high DPI screens, the whole UI scales nicely when increasing the
font size, except for the attitude widget, that was limited to 200 pixels.

Allow resizing pip window

LogDownloadController: only skip entry if size==0 && APM firmware

save to kml use double number with 10 valid digits。

Update joystick mapping database

Make FTP more robust

Move to Qt 5.9.1

Assume all vehicles support MANUAL_CONTROL

On PX4, under certain circumstances and in rare cases, there can be log
files with 0 size. In that case QGC ignored the entry and tried to
re-request the entry indefinitely.

If there are dropped packets during a burst download, the offsets and sizes
of the missing chunks are stored in a queue, and after the burst is
completed, they're requested individually.

This stores the last request and resends it after a timeout, with a max
of 6 retries.
It also checks for old incoming packets and drops them.

PX4 Firmware add DO_SET_ROI

Fix sub frame parameter download text overflow

Fix text overflow on sub safety page

Allow user-selectable brand image

Add ROV flightmap image for Sub to differentiate from boat.