Resolve "Importing a vtk file"

I did my contribution for the issue #3115. I have added the logic in readVTK function to read the physical labels from CELL_DATA and now the list of physical labels are visible in Tools -> Visibility -> Physical groups. I converted the few .geo files to .vtk from tutorials directory to test the function. Coming to the attached .vtk file attached by the issue reporter in the issue, the line after CELL_DATA is SCALARS CellEntityIds int. After I changed it to SCALARS CellEntityIds int 1, the physical labels are visible with the updated code