install vtkpython and pvtkpython once again

Note, the functionality of vtkpython is pretty broken (as it was in 5.x)
It can not find your vtk python modules in many cases unless they are
in a handful of default sytem install locations. In that case you are
better off just running the normal python interpretter.

pvtkpython is somewhat more useful in that it adds auto initialization
and shutdown of MPI.

Change-Id: I5e42b25bfb34bee104e75d08d2fa15312ee57a31
Merge topic 'restore_vtkpython_install_rule' into master

d8e8502a install vtkpython and pvtkpython once again