Report small changes in tasks that will cause resubmission

[Samreay]

Sometimes tasks get resubmitted when we dont expect them to. Given that we dont clobber the prior tasks output directory right away, it should be possible to compare the newly generated config files with the existing ones, and then show the differences between them. Getting this diff can be done simply using difflib

This is most important for sims (as they will kick off everything), but Id start with biascor for faster iteration, then do snana_lcfit and then finally snana_sim. The sims are the most complex case because we have multiple input files, but thats just one extra for loop.