JSON diff has unreasonable threshold for big diff

[jmarrec]

As stated on NatLabRockies/EnergyPlus#8833 (comment)

The json big diffs: I think the epregression script is unreasonable: https://github.com/NREL/EnergyPlusRegressionTool/blob/237b8a38c280fd0ce6563b6849ae51376e326d66/epregressions/runtests.py#L630-L643

It assumes an absolute difference > 0.0001 is a big diff. This for eg:

It's categorized as a big diff, but in fact it's a 1e-12 difference in %...

In [1]: f_1 = 30310597.103115804

In [2]: f_2 = 30310597.102913737

In [3]: abs(f_1 - f_2) > 0.00001
Out[6]: True

In [7]: (f_1 - f_2) / f_1
Out[7]: 6.6665528125937005e-12