expose setting of max-steps to python interface & test

[skyreflectedinmirrors]

Changes proposed in this pull request:

• Expose the ability to set the maximum number of CVODEs steps to the python interface
• Add test to ensure setting works correctly.

I am using Cantera (as typically) to validate other ODE solvers. As such I typically want to set the network reactor tolerances to very stringent values (e.g., atol=1e-20, rtol=1e-15) and run ignition problems over a wide range of conditions.

The issue I'm currently facing is that the default # of steps (appears to be 20k?) works for most cases, but not all. Rather than playing the game of trying to modify the tolerances to fit in the number of steps, it would be nice if we could just expose this property to the user via the python interface.

Let me know if there are any comments / concerns,

Best,

Nick

[codecov]

Codecov Report

Merging #581 into master will increase coverage by 0.01%.
The diff coverage is 33.33%.

@@            Coverage Diff            @@
##           master    #581      +/-   ##
=========================================
+ Coverage   67.69%   67.7%   +0.01%     
=========================================
  Files         362     362              
  Lines       38456   38459       +3     
=========================================
+ Hits        26031   26039       +8     
+ Misses      12425   12420       -5

Impacted Files	Coverage Δ
include/cantera/zeroD/ReactorNet.h	0% <ø> (ø)	⬆️
include/cantera/numerics/CVodesIntegrator.h	0% <ø> (ø)	⬆️
include/cantera/numerics/Integrator.h	2.85% <0%> (-0.18%)	⬇️
src/numerics/CVodesIntegrator.cpp	73.54% <100%> (+2.83%)	⬆️

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[bryanwweber]

Hey @arghdos! Thanks for this. Can you also add a method to get the max steps as well? Does CVODES expose that information?

[skyreflectedinmirrors]

@bryanwweber Hmm, it doesn't look like they allow you to query the maximum # of steps, however we should be able to just return whatever value is stored in the integrator.

[skyreflectedinmirrors]

@bryanwweber -- implemented

[speth]

I had just a few minor suggestions, but this generally looks fine to me.

[speth]

Sorry, I didn't notice that you updated this. LGTM!