Merge remote-tracking branch 'origin/feature/6773_calculate_peaktof_getei2'
Set peak time to zero in GetEi if no peak is found. Refs #6782

Also set initial value of Tzero to 0.0 so that if ei is fixed, this is
the set to 0 automatically.
Merge branch 'feature/6782_getei_peaktime_error' into develop