Hermes-3 unnecessarily recalculating metric coefficients by default and erroring with nonorthogonal grids

[mikekryjak]

There is a setting called loadmetric which recalculates the metric coefficients based on R,Z etc:

hermes-3/hermes-3.cxx

Lines 204 to 207 in 88aa8c6

	if (options["loadmetric"]
	.doc("Load Rxy, Bpxy etc. to create orthogonal metric?")
	.withDefault(true)) {
	LoadMetric(rho_s0, Bnorm);

This was done for back when Hypnotoad wasn't saving metric coefficients to file. It is enabled by default. When reading a nonorthogonal grid, it creates an error of the kind g22 is non finite at (0,2) - this is because the reconstruction calculation assumes orthogonality.

The option should be disabled by default as Hypnotoad saves the metrics now.
Enabling it should print a warning that the metrics will not be compatible with nonorthogonal grids.

Thanks @mrhardman and @bendudson for diagnosing this.

[bendudson]

Time to resurrect PR #87