Remove legacy code from plasma/properties/base.py
Remove legacy code from plasma/properties/base.py

Fix BaseAtomicDataProperty:calculate():
    It won't try to load atom_data._<property> anymore since.
    This is a cleanup since atom_data._<property> doesn't exist anymore.

orbitfold/tardis,Tobychev/tardis,kaushik94/tardis,orbitfold/tardis,Minhmo/tardis,kaushik94/tardis,kaushik94/tardis,orbitfold/tardis,Minhmo/tardis,Tobychev/tardis,Tobychev/tardis,orbitfold/tardis,Minhmo/tardis,kaushik94/tardis