Optimize and fix handling of stimulus species assignment
This MR proposes three changes for bench:
- Fixing ratio handling (
--stim-ratios
). So far theiIon
was incremented in the loop and the first ratio was assigned to all species as far as I can see - Parsing of
--stim-species
and--stim-ratios
only once and not per timestep - More explicit documentation of
--stim-start