Define the generic format in a separate file

[jan-janssen]

To make the code more human readable, I introduce atomistics/shared/generic.py, which defines the output keys in a human-readable way. For example for the static calculation:

static_calculation_output_keys = (
    "forces",  # np.ndarray (n, 3) [eV / Ang^2]
    "energy",  # float [eV]
    "stress",  # np.ndarray (3, 3) [GPa]
    "volume",  # float [Ang^3]
)

In atomistics/shared/output.py the data classes are then generated using dataclasses.make_dataclass.