Add Lorentz force for charged classical particles

Heiko Appelrequested to merge
333-Add-Lorentz-force-for-charged-particles into develop

Description

This MR adds the classical Lorentz force for charged particles to the multi-system framework.

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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.

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