Improved workflows for model debugging

[paulromano]

While OpenMC has some ability to provide information about lost particles in a model, this information is of limited value to analysts to actually determine the root cause. Our team will automate the process of 1) identifying what areas in a geometry may be causing problems; 2) visualizing overlaps, gaps, and other flaws; and 3) providing one or more suggested fixes in order to address the underlying problem.