Support for Point 2d set

[philippeVerney]

Is your feature request related to a problem? Please describe.
I need to transfer a point set where points are described by X, Y and a property value.

Describe the solution you'd like
I would like to avoid to have to write Z since I have not this information.

Describe alternatives you've considered
Using Point 3d set and put NaN in all Z values

Additional context
RESQML2 allows that using the point2darray instead of the point3darray