[vtkusers] Stereograpic sphere

[David Thompson]

Hi Luis,

Please keep vtkusers included in replies so that others can benefit.

> There are assigned  const char* projName = "rouss"; rouss means? Sorry about that.

Rouss is short for Roussilhe. See https://en.wikipedia.org/wiki/Roussilhe_oblique_stereographic_projection .

If you build VTK with the geovis kit enabled and run TestGeoProjection, it will print a list of strings that can replace "rouss". They are other projection names.

	David