add output to ERP that is similar to outagesim resilience_by_time_step (which has # hrs can survive, for each start time)

[hdunham]

The outage simulator output resilience_by_time_step is useful and missing in the ERP. Due to the probabilistic nature of the ERP we cannot return that exactly, but can perhaps do better than the current quartile outputs that go into the box and whisker plot in the UI. Can we do expected duration can survive for each each outage start time? Or quartile/box-whisker vals for this instead of/in addition to for survival prob?