This commit performs a first pass at implementing more realistic helicopter
physics particularly at low speeds due to rotor effects:

- Improved heading changes when pitch/banking, ported from @metiscus fork
- In-Ground-Effect (IGE): thrust boost when close to ground
- Transverse Flow Effect: roll,bank effects between 5-25 knots
- ETL: thrust penalty below 24knots, roll-bank effects
- Torque: heading changes at lower speeds + higher collective

The effects make landings more realistic and challenging.

I had added a rotor_diameter model option, but the models already define
rotors and their diameters using "rotor_new".

The only combination that serves to differentiate and count main rotors is
that they either have "follow controls" set or they are "tiltable" (ospray).

When more than 1 main rotor is identified (v22, ka-25), then torque and
Transverse Flow rotor effects are compensated and disabled.

…lism