reimplement parameter distribution
Overall goals
- Restore outcommented examples
- Support Monte-Carlo integration over all parameters [Redmine697]. -> #539
- Improve examples [Redmine1014].
- Support arbitrary functions (random variable -> model parameters); requires alternative Py bindings (#232 (closed)).
Immediate steps:
- rm m_beam and m_axis from *Sim (!1454 (merged))
- ready to go for Par-based generic mechanism?
- apply the same to SpecSim