Geometry_Engine: Switch IsCoplanar from numerical solution to fitting plane and checking distance to it

[pawelbaran]

Description:

Recently (in #3283), collinearity check has been changed from numerical solution to a geometrical one, i.e. instead of computing matrices of point coordinates, a line is fit in point set and then each point is checked whether it lies within tolerance from that line. This change improved precision and robustness of the method, so I believe it would make sense to do similar with IsCoplanar.