Hypnotoad: add checkbox to output metrics for orthogonal coordinates

[johnomotani]

Add a checkbox to the 'Output' tab, which if selected outputs metrics for orthogonal coordinates (i.e. using ShiftedMetric), by setting the integrated shear to zero, I=0, when calculating the metric components.

[bendudson]

This raises a point: Should grid files have some flag which specifies what kind of coordinate system they contain? Particularly if the g** fields are given, then these should be for shifted metric or field-aligned etc. Some kind of mesh type identifier, probably with a version number for forward compatibility. This should either specify what paralleltransform is, or at least there could be a check for consistency.

[johnomotani]

I think grid files should say what type of coordinates they use for g**. I've had a stab at adding a flag to the grid file to specify the type of coordinates: hypnotoad-shiftedmetric-output...hypnotoad-shiftedmetric-output-coord-system-labelling.

That branch uses 'generic' labels. It adds a coordinates_type to the gridfile (as an attribute, because that's how netCDF prefers to deal with strings), which is allowed to take values of "field_aligned" (for ParallelTransformIdentity, "orthogonal" (for ShiftedMetric) or "fci" (for FCITransform). Would it be better to be BOUT-specific and use instead something like paralleltransform={"identity","shiftedmetric","fci"}?

Agree some kind of version numbering would be good. We could:

1. Write the commit hash to the grid file
2. Write a version number for Hypnotoad, like '1.0.1' as an array of ints, and update the version number manually when we update Hypnotoad.

2's easier to check if the version is newer/older than something, but I don't see a way of making it automatic. Any preferences or other options?