Implement particle generation model for thermal rest gas motion
The velocities emerging from the thermal rest gas motion are inherited by the ionization products. The model requires the temperature of the gas and the mass of the gas particles:
PhysicalQuantity('Temperature', unit='K')
PhysicalQuantity('Mass', unit='kg')
The velocities are sampled from the Maxwell–Boltzmann distribution.
Allowing specifications of the mass in units of the unified atomic mass unit is convenient.
This model contains only functionality for the momentum generation and therefore would benefit from #160).