confTool: ignore numeric difference in nested lists

Ignore numeric differences in nested lists, e.g. the following diff

  PtBins =  [[0, 1.05, 1.5, 2.0, 9.9]]  vs  [[0.0, 1.05, 1.5, 2.0, 9.9]]   <<

is now marked correctly as "known difference".

Relates to ATR-28500, cc @tbold @khoo.