Create variableHandler from configuration file automatically

[isorrentino]

It would be nice to have the possibility to create the variableHandler object by loading parameters specified in a configuration file, instead of reading each parameter per time and initializing it by hand.

cc @GiulioRomualdi @S-Dafarra

[S-Dafarra]

I am not sure I understood. Can you give an example of expected behavior?

[GiulioRomualdi]

I think @isorrentino was referring to adding an initialize method that takes a parameter handler and adds all the variables