Colabfit enhancments by Eric

[ipcamit]

This PR consists changes made by Eric to colabfit io. List of changes:

Edited functions:

1. Dataset.from_colabfit
2. Dataset.add_from_colabfit
3. Dataset._read_from_coabfit
4. Configuration.from_colabfit

Added functions:

1. Configuration.to_ase_atoms: converts KLIFF configuration to ASE atoms configuration. Used for storing the KLIFF dataset back to Colabfit.

Other changes:
using from chemical_symbols ase.data

[mjwen]

the order of ase_atoms_list, and path should be switched in

instance.add_from_ase(
            ase_atoms_list, path, weight, energy_key, forces_key, slices, file_format
        )
        return instance

as well.

It is called in from_ase method. See #161

[mjwen]

Are we planning to add tests for this class, so that we can avoid such bugs?

[ipcamit]

Yes. Next PR would be of tests for this and transforms modules. It was on hold has I had to fix the descriptor library first. Finished it this week, so KLIFF tests are next.