MTZ sanity checker?

[DHekstra]

Abandoning #49 . The main issue there was that upstream user errors can cause duplicate Miller indices or Miller indices outside of the primary ASU coming into difference map calculations. It would be appropriate to detect these issues before going into diffmap.py and internaldiffmap.py.

Perhaps we could have a MTZ sanity check script containing these basic checks and, perhaps, others

        for _,(_ds, _ds_name) in enumerate(zip(datasets, dataset_names)):
            print(f"\nChecking {_ds_name}.")
            dup_sum  = np.sum(_ds.index.duplicated())
            if dup_sum  > 0:
                print(f"{_ds_name} contains {dup_sum } duplicate entries.")
            if not np.all(rs.utils.asu.in_asu(np.array(_ds.index.to_list()), _ds.spacegroup)):
                print(f"Some Miller indices of {_ds_name} are outside of the primary ASU.")