write a DiffractionObject serializer/deserializer

[sbillinge]

Problem

It would be great if we could dump and load DiffractionObjects as DiffractionObjects

Proposed solution

either use json, but maybe better, figure out how to do it with an hdf5 file to preserve the numpy arrays correctly, but also all the metadata.

Maybe save the file with a dfpydo extension or sthg like that. This would allow DiffractionObjects to be shared more easily, with all their metadata.