Configuration of the VTK output.
These are the settings, that can be configured by the user with respect to the VTK output.
Format in which the data is present (either 'ascii' or 'binary')
If a timestep output is done, the filename can either be built with the simulation time or the iteration.
If this flag is set to true, iterations will be used, otherwise the simulation time (which is the default).
Flag to decided whether to write pvd file or not. Default is true.