New feature: Visual Debugging

[wtraylor]

It could be helpfulto have a live rendering of the herbivore populations while the simulation is running. I suggest the term Visual Debugging from Grimm (2002).

I see two ways to realize it:

1. Read the textfile output during the simulation.
2. Add an output writer that pipes the output directly to a visualizer.

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Grimm, Volker. "Visual debugging: a way of analyzing, understanding and communicating bottom‐up simulation models in ecology." Natural Resource Modeling 15.1 (2002): 23-38.