Yaw Damper implementation

[iandareid]

The yaw damper combats adverse yaw. It is a washout filter that counteracts the high frequency yaw resulting from the adverse yaw.

[iandareid]

The yaw damper is implemented. I also changed the saturation code to warn you of bad input. Perhaps this is something we should put in the style guide? Essentially if you create a function it should warn about invalid input?

In any case the yaw damper works and is integrated. It is VERY reliant on matching the Aerodynamic coefficients if the washout filter gain y_kr and filter bandwidth p_wo to work. (See the UAV book chapter 6 section on Yaw Damper for more). We should at some point add documentation on how to tune yaw damper in the absence of a good aero model.