change internally the use of plane by the use of a normal to plane

[volodia99]

It would probably be better to use classes to handle geometry transformations (from _native_geometry (spherical, cylindrical, cartesian) to a new geometry (spherical, cylindrical, cartesian), with a projection/slice in a specific plane)

choosemean/chooseslice -> easy (plane->axis)
but for the rest, the implementation needs to be completely different

• implement when different _native_geometry