CoordinateSystem.axes_names -> CoordinateSystem.axis_names

[kevinyamauchi]

I think it makes more sense grammar-wise to if we call them CoordinateSystem.axis_namesinstead ofCoordinateSystem.axes_names`.

[ivirshup]

I think the CoordinateSystems should have a public axes parameter to just get the axes. Not sure why this is private at the moment.

But then, I think I like:

cs.axes
cs.axes_names

Better than:

cs.axes
cs.axis_names

[LucaMarconato]

@melonora and I agree with @ivirshup, so we just need to

• [ ] add axes() to the NgffCoordinateSystem class.