Feature request- save per-well aggregates

[bethac07]

CPA calculates per-well aggregates in multiple modules, notably Classifier and Plate Viewer. It'd be nice if the user could export per-well (mean, median, sum) data to a table or CSV easily in a similar way; in fact it feels so much like it belongs in CPA that more than once I've opened CPA to do this before remembering that CPA, well, doesn't do that 😆 . I know to some degree it infringes on cytominer's "territory", but I wonder if it might not be nice to have it here too.

[jhung0]

checkout b42f901