Add support for labelled arrays

[LukeWeidenwalker]

• array_labels
• array_find_label (optional in core profile)
• array_create_labeled (optional in core profile)

We'll need to figure out how we can support labelled arrays. It's easy for datacubes, there the labels are just the xr.Dataarray coordinates. But how do we get these down into child processes? E.g. an apply_dimension wrapping array_labels, all that's currently ending up in array_labels is the raw numpy array without the labels.

[clausmichele]

NotImplementedError: labelled arrays are currently not implemented. Please use index instead.

I encountered this error trying to compute the NDVI passing the bands labels to the array_element process.

Is there some development going on to solve this issue?

[LukeWeidenwalker]

No, we're not currently working on this!

[clausmichele]

Implementation is in this PR #155