[accel-momentum] Rolling control adjustments

I may as well submit this since I went through the trouble of figuring out the roll speed loss math before anyways.

Changes from accelmomentum latest:

1. Rolling doesn't lose speed on flat ground
   
2. Spin control reduction never applies in the air, because of this the PF_THOKKED hack for full control was removed
   
3. Improved ability to course correct while rolling on the ground

7/10/2021 latest exe: srb2-am-spin.exe