Add irreducible infeasibility set (IIS) calculation

[jajhall]

Adding irreducible infeasibility set (IIS) calculation is great fun, and a good test of the simplex solvers

[jajhall]

@galabovaa Definitely not for the new release! The CI failures that I've created look odd

[kbrix2000]

@jajhall Very helpful feature, thank you very much!

Can I try IIS calculation already right now? I tried setting the option iis_strategy but did not see any effect. Is it possible to access IIS calculation from the command line?

[jajhall]

Can I try IIS calculation already right now? I tried setting the option iis_strategy but did not see any effect. Is it possible to access IIS calculation from the command line?

Sorry, no, I added iis_strategy in development, but this PR is just allows the feasibility-relaxation calculation - for which the first step of IIS calculation is a special case.

[kbrix2000]

Thanks for your quick reply. Ok, I see.

Just let me know if you need another beta tester.