* Fischer distribution sampling added
* transform method has norm kwarg to normalize tranformed vectors
* axisangle property to calculate axis and angle from rotation matrix
* StereoNet arc method added
* Vec3 and Group upper and flip properties implemented
* DefGrad, VelGrad and Stress rotate method accepts also rotation matrix
* velgrad method added to DefGrad to calculate matrix logarithm
* StereoGrid has new methods max, min, max_at, min_at