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

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.

Add basic KML functionality

Guided takeoff

Better plan load signaling

Joystick: add a button to support negative thrust

VisualMissionItemTest.h: Remove lost trailing spaces

MissionItemStatus: Show survey and others complex items as chars