Merge StackedCoordinates and DependentCoordinates

[jmilloy]

Description

The DependentCoordinates are a generalization of StackedCoordinates that supports N-dimensional stacked coordinate arrays. It is confusing to have both, and also to have both the lat_lon and lat,lon dimension names.

The DependentCoordinates takes a list of numpy arrays, whereas the StackedCoordinates takes a list of Coordinates1d objects, so that needs to be sorted out as well.

Note also that ArrayCoordinatesNd is a direct generalization of ArrayCoordinates1d, so ArrayCoordinates1d should probably be removed/replaced as well.

Proposal

I would use ArrayCoordinatesNd directly in the DependentCoordinates (instead of a numpy array). UnformCoordinates1d would need a generalized version as well, and if we use N-dimeesional origin, corner, step, and shape traits/properties, that will correspond well with RotatedCoordinates. The clinspace spec would need to be modified, too.

And then I think we should rename DependentCoordinates to StackedCoordinates (and remove the current StackedCoordinates).

I don't think it matters to me whether we use lat_lon or lat,lon as the dimension name.

[jmilloy]

@mlshapiro @mpu-creare We've both discussed this at some point.

[mpu-creare]

@jmilloy Is this done?

[jmilloy]

It is now! I just removed a few stray references to DependentCoordinates. I'm guessing that's why I didn't close this earlier.