update update script for xdmf3 latest
update update script for xdmf3 latest

mostly be sure to copy over new files added to xdmf3 since last
import, but also slip a .gitattributes as we extract to prevent
VTK merge requests from complaining if xdmf doesn't match VTK's
style rules

keithroe/vtkoptix,SimVascular/VTK,SimVascular/VTK,keithroe/vtkoptix,keithroe/vtkoptix,SimVascular/VTK,SimVascular/VTK,SimVascular/VTK,SimVascular/VTK,keithroe/vtkoptix,SimVascular/VTK,keithroe/vtkoptix,keithroe/vtkoptix,SimVascular/VTK,keithroe/vtkoptix,keithroe/vtkoptix