Refactor config_dict properties

[haneug]

Is your feature request related to a problem? Please describe.
Output getters for config_dict properties have to check whether config_dict is None. This can be a bit lengthy. We should add a dedicated class which contains the dict and handles this logic. Also, negative gbw_index should result in returning None.

[haneug]

If config_dict is used it should include the gbw JSON file defaults:

config_dict = {
    "Basisset": True,          
    "MolecularOrbitals": True
}

[timmyte]

If config_dict is used it should include the gbw JSON file defaults:

config_dict = {
    "Basisset": True,          
    "MolecularOrbitals": True
}

It's generally dangerous to hard-code another programs defaults into your own wrapper, as they might change without notice. It's best to let the program determine its own defaults.
If this is by the design of orca_2json not possible, we have to swallow that pill.
But please take that into consideration.