Investigate improved handling of Zeno behaviour

[ralfgerlich]

Zeno behaviour occurs when zero-crossing events (and associated changes of system state) occur at ever-decreasing time-distances from each other. This may lead to stalling the progress of simulation time.

So far, we detect excessive occurrence of zero-crossing events, and throw an exception if this occurs. However, there are strategies for resolving some types of Zeno behaviour. An overview is given in https://doi.org/10.3182/20080706-5-KR-1001.01346 (thanks @albert-mathews for pointing this out).

Implementation of these strategies in MoDyPy should be investigated.