Start to address #84

This change addresses the main underlying problem behind #84 (closed): If you restart a simulation run after changing the simulation config (especially the number of scenarios or replicates) it would reuse the existing scenario params table that was already generated, rather than generate a new one.

Currently we don't have a great way of indicating that a simulation run for a specific configuration completed (this might be a topic rich for discussion, but for another time).

So this at least works around the initial problem. Unfortunately it will overwrite without confirmation. Usually (in the case of the "common mistake" described in #84 (closed)) this will be fine.