Changes:

• A custom implicit solvent may be defined for the Turbomole input creator through
  its dielectric constant and probe radius.
• Turbomole calculator can now carry out Hartree-Fock calculations.
• Orca calculator can now carry out broken-symmetry DFT calculations.
• Improve comparisons of periodic data structures.
• Ease communication between forked processes for monitoring calculations.
• Various bugfixes and improvements
• Added data structures for interfacing with integral libraries.
• The BondDetectors can alternatively rely on Van der Waals (VdW) radii instead of covalent radii.
• The PeriodicSystem generates its bond orders now per default based on VdW radii between solid state atoms.
• Turbomole calculator can now calculate excited states.
• The PdbStreamHandler can read multiple models in a pdb file (encoded by the MODEL tag in the file).
• Add Python bindings for D3/D3BJ dispersion corrections.
• Add additional setting to external QC calculators that allows to enforce the set SCF convergence criterion.
• The pressure for free energy calculations may now be changed. Current default 1 atm.
• Add Spglib dependency.
• Increase pickle support of Python bindings.
• Optimization related setting names are gathered in a separate namespace and removed from the optimizers