Fix dangling pointer access

main: Returning critical messsage and an error code when QGC is alredy running

Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>

Adding RTP UDP h.265

* 'rtpUdpH265' of https://github.com/mavlink/qgroundcontrol:
  Added udp265 gstreamer pipeline

Revert ParameterEditor to QtQuick.Controls 1.x

QtQuick.Controls 2.4

Update all files that use a QML Menu item to QtQuick.Controls 2.4 to solve the issue of a menu showing up in random places on Android.

Custom Build Example

Move fly view away from background and into main window. The size different was causing the map not to match the one in plan view.

Move PreflightCheckList to custom builds only. The model, which used to be implemented within BuiltinPreFlightCheckModel is now within the control itself. It is up to the implementer to define a proper model.

Adding VTOL Octoplane airframe type

Stable merge