Draft: Allow TET14 via IOSS Reader

Hi,

If I read a TET15 mesh with Paraview using the IOSS Reader, would I be correct in assuming (I don't have such a mesh to debug with) that in vtkIOSSUtilities::GetConnectivity() it essentially gets reduced to a TET4?

There's functionality specific to TET15 in both vtkLagrangeTetra and vtkHigherOrderTetra so I'm a bit confused.

I ask since if I allow TET14 to be classified as VTK_LAGRANGE_TETRAHEDRON as if it were a TET15, it seems the functionality in vtkHigherOrderTetra is called for TET4, but neither Paraview or VTK complain and the data seems to plot, even though the reported number of nodes is incorrect.

Cheers, Nuno