Discrete phase model

Setting up and querying the model

>>> dpm = solver.settings.setup.models.discrete_phase
>>> dpm_models = dpm.physical_models
>>> dpm_models.virtual_mass_force.enabled.get_state()
>>> dpm_models.virtual_mass_force.virtual_mass_factor.is_active()
False
>>> dpm_models.virtual_mass_force.enabled.set_state(True)
>>> dpm_models.virtual_mass_force.virtual_mass_factor.get_state()
0.5