joystick mode ui option

this adds an option to select the mode of the joystick in the joystick
config widget. The mode sets the setpoint type which is sent when moving
the joystick.
Merge remote-tracking branch 'upstream/mavlinksubmodule_joystickinput' into mavlinksubmodule_joystickinput

Conflicts:
	src/uas/UAS.cc