fix: Add python-vtk6 as dependency for libvtk6-dev on Ubuntu 16.04
fix: Add python-vtk6 as dependency for libvtk6-dev on Ubuntu 16.04

BioMedIA/MIRTK,schuhschuh/MIRTK,BioMedIA/MIRTK,schuhschuh/MIRTK,BioMedIA/MIRTK,schuhschuh/MIRTK,schuhschuh/MIRTK,BioMedIA/MIRTK