Request: Calibration / scaling for joystick control

On a most current RC controllers you can set the trim point and range so that, for example, full stick travel only gives you a PWM output between 1350 and 1650 (rather than 1000-2000). If you're using a joystick through MP, you can clip your output using the RC_MIN and RC_MAX for a channel, but that's it.

It would be handy to be able to check a box for clip vs. scale for the joystick axes. i.e. for an RC_MIN/MAX range of 1400 ro 1600, if I select "clip", then I'd hit 1600 at +20% stick movement and it would stay at 1600 no matter how far forward I pushed. With "scale", at +20% stick movement I'd get 1520 PWM output, and only hit 1600 at full stick.

It's really come up since I started playing with my 1/16 RC car, which I want to run at about 20% throttle at most. with the current setting, it's basically on or off based on how little stick movement gives me the max throttle I'm after. The cats at home are NOT happy!!

Start by locating Mission Planner's joystick-axis handling and the code that applies RC_MIN and RC_MAX to channel output. Compare the requested clip and scale behaviors, then verify that selecting either mode produces the stated PWM ranges for partial and full stick movement.

Written by the indexing model from the issue text.