In review it was requested to have a different name for
manual_control_setpoint.z because of the adjusted range.
I started to investigate what naming is most intuitive and found
that most people recognize the stick axes as roll, pitch, yaw, throttle.
It comes at no surprise because other autopilots
and APIs seem to share this convention.
While changing the code I realized that even within the code base
the axes are usually assigned to a variable with that name or
have comments next to the assignment clarifying the axes
using these names.
To be consistent with all other axes of stick input and avoid future
rescaling confusion.
Note: for the MAVLink message 69 MANUAL_CONTROL it's using the full range
according to the message specs now [-1000,1000].
