The idea is to later define chains of module in the input script by
setting an input and output field and the according function to call.
Currently, the code is not ready for such a chain, but the change is
done in advance.
It is now possible to run a simulation for one iteration in sequential
mode without the use of Rmufits.
According scripts are provided.
refactor: TransportSim renamed to DiffusionModule
refactor: parsing of R input script is now done outside of simulation
modules (except ChemSim)