Draft: Add CFM4 propagator with moving ions and gauge field
Description
Apply Hamiltonian separately for both times inside Hamiltonian to capture all features (ions, gauge field, phases, ...). This makes it slower because the full Hamiltonian is applied twice per operation inside the exponential, but at least all terms are treated correctly.
News snippet
Add CFM4 propagator with moving ions and gauge field
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.