HDF5 integration for the Property framework

[mrossinek]

What is the expected behavior?

The Property framework will be mostly finalized and properly integrated with the drivers by closing #264 (PR link TBD).
Due to time constraints, the HDF5 integration will not become part of Nature's upcoming 0.2.0 release. The most important reason that it will require some more planning, which should be done in this issue (to be updated later).

For the time being, the (soon to be) deprecated qiskit_nature.drivers.QMolecule object can be stored and loaded to/from HDF5 files and subsequently converted to the Property framework as follows:

from qiskit_nature.drivers import QMolecule
q_mol = QMolecule("path/to/file.hdf5")
q_mol.load()

from qiskit_nature.properties.second_quantization.electronic import ElectronicStructureDriverResult
property = ElectronicStructureDriverResult.from_legacy_driver_result(q_mol)

The HDF5Driver from the qiskit_nature.drivers.second_quantization module may be used for the exact same purpose as shown above.