adding nice pretty lines and start and stop of simulation
Merge branch 'minimal-spiking-mt' of https://github.com/bernhardkaplan/bcpnn-mt into minimal-spiking-mt

* 'minimal-spiking-mt' of https://github.com/bernhardkaplan/bcpnn-mt:
  Re-ADD: plot_hexgrid.py resurrected from the pet-cemetary