Allow to silence VTK output

Description

The current program always write vtk files independent if the program is being used as stand-alone or if it's being used for the GUI. The idea hence is to allow to switch vtk output on and off.

Proposal

Add a new keyword in the ini file to switch on/off vtk file outputs.

How to test the implementation?

Add a python wrapper to check that vtk output was/wasn't generated by running a program with the two options

Related issues

See #