Generalized Kohn-Sham and MGGA from OEP

Description

Introducing a new run method, generalized Kohn-Sham, for running hybrid functionals and MGGAs. This replace the Hartree-Fock mode for the hybrid functionals. The MGGA can now be treated using the OEP framework, simply adding TheoryLevel = kohn_sham to the input file.

News snippet

Introducing a new run method, generalized Kohn-Sham, for running hybrid functionals and MGGAs. The MGGA can now be treated using the OEP framework.

Checklist

• I have checked that my code follows the Octopus coding standards
• I have added tests for all the new features added in this request.