Saving and reading states

It should be possible to save and read states/objects, such as the material parameters, the mesh or any result obtained from a numerical experiment. Something like

material.save("filename.json")

which could save the material to a json file. It would be good if we could make it such that the material parameters are saved in a compressed form, i.e., if a material parameter is not global but the factual values is constant, then it only saves a single number/vector.

Problems for all this savings are of course the coupling between the different classes.