Include "step" always in output

[bachl]

Hi, first of all, thank you for a really cool package!

I have just I minor suggestion: At the moment, the definition of agent_reports or eval_criteria causes the output not to include the step_measures. I would find it much more convenient to always include all defined measures at all levels in the output. This can be easily done by changing two lines of "nlrun.R". I have made the changes in a fork (https://github.com/bachl/nlexperiment/blob/master/R/nlrun.R) and can provide a pull request, if this is more convenient for you.

Best,
Marko

[bergant]

In case of agent step reports, I agree. However, when evaluation criteria is used, additional information by step could require a lot of additional memory in the result structure. I'll add an option in the experiment creation (keep_step_measures = TRUE) when evaluating simulation with criteria function.

[bachl]

Cool, thank you!