[Gzz] RD texture visualization

[Tuomas Lukka]

Janne: when visualizing the 3D blocks, you should know that
there are LOTS of existing tools that do this well, for example
vtk which we used with CAs. Having the computation and vz'n in
separate processes would also give better response to user actions.

Since we will be investigating more 3D textures, it might be worthwhile 
to start using vtk.

        Tuomas