Decide on interaction in main loop

[TobiasWinchen]

The independent decision on interaction in every module can be problematic in cases of processes with similar cross section as the order of interactions begin to matter. A decision in the main loop would be preferable as this can be avoided completely. However, this has so far not been an issue with existing use cases and have been studied in this thesis, chapter 4.1. The resulting error of the effective interaction probability is less than p² < 1% with the default choices.