Merge branch 'joystick_commands' of github.com:Susurrus/qgroundcontrol into joystick_commands

Conflicts:
	src/input/JoystickInput.cc
	src/input/JoystickInput.h
	src/ui/JoystickAxis.cc
	src/ui/JoystickAxis.h
	src/ui/JoystickAxis.ui
	src/ui/JoystickWidget.cc