Add Cmq, the pitch rate dependand contribution ot the pitching moment to the model

[ufechner7]

Currently oscillations around the y axis are only dampened by the bridle, but not by the aerodynamics of the kite itself. There is no aerodynamic force acting on the nose. This can lead to oscillations and should be changed.

See also: https://www.perplexity.ai/search/how-is-cmq-the-pitch-rate-cont-mwrDxAliRcajIQs3WrKo7A

• add pitch stability test
• add Cmq and cord_length to the settings struct
• calculate the pitch rate
• add a damping_force that is acting on A in one direction and on C and D in the opposite direction

[ufechner7]

The following formula for the damping force is used:

   f_d = 0.5 * rho * s.set.area * norm(va_xz1)^2 * (s.set.cmq * s.pitch_rate * s.set.cord_length) * z

with z being the normalized z vector of the kite reference frame and va_xz1 the apparent wind speed in the xz plane and the nose of the kite.

[ufechner7]

Works fine now.