Testing with Pydgin

[tomcl]

For more flexibility in the future it would be good to modify VisualRandomTestGen to use Pydgin simulators: https://github.com/cornell-brg/pydgin.

That would make it easier to test arbitrary instruction sets.

I suppose also a more long-term project would be to re-implement Pydgin simulators directly in Visual2 so that Pydgin definitions could directly generate instruction parse and simulation.