Add boat/rover flight mode info

[hamishwillee]

First part of fixing #1025.

@Jaeyoung-Lim Some questions :-)

1. How are sticks mapped in mode 2/other modes? - below is for forward-flying aircraft

   
   

   My assumption is that probably we simply map throttle and turn left/right. The throttle behaviour depending on whether the vehicle support reverse. You could obviously control it from just one spring loaded stick.

2. Further, I assume that releasing the sticks is much like the behaviour on MC altitude mode. The motors turn off and wheels/rudder center. However there might still be momentum so the vehicle will continue until that dissipates. On a boat it will likely drift. Is that correct?

3. Is there a center-dead zone on the sticks like in position mode?

In mission mode, what is the behaviour like?

• What mission commands are supported vs unsupported? Can you use the camera?
• What happens if something is unsupported? i.e. say I use VTOL takeoff, will that work or just be ignored. Say I have no takeoff? What about land?
• What is the loiter command behaviour for a rover? I presume it is just waits at point for time? What if it gets an FW lointer for N turns command?
• What is the loiter command behaviour for a boat? Is it like FW where you circle the point, or does it go inside the radius and wait? If it drifts out, does it then try to move back into the radius?
• What is path if we exit loiter (assuming FW type loiter - ignore if it isn't)
• What is the waypoint entry/output behaviour? i.e. on an MC we fly mostly to the point, then do a sharp turn towards next point (well, now we do a rounded turn, but you get the point). On FW we fly a path that takes us around waypoints within a radius.
• Will it still obey avoidance setpoints from an offboard system? (ie does obstacle avoidance work).
• What does it do with altitude setpoints in missions? Ignore?

I can try some of this in simulator, but I figure you can give me a quick confirmation of much of this first.