Migrate SNTChart customizations to scijava-plot

[tferr]

Now that the scijava plot is officially released, it would be better to move SNTChart tweaks there, so that the entire scijava stack can profit from them. Mainly, one should take the 'theme' customizations of category plots in SNTChart, and move them upstream to scijava-ui-swing.

For reference, this is how SNTChart renders some category charts:

See initial discussion at : scijava/scijava-plot#5 (comment)

[imagesc-bot]

This issue has been mentioned on Image.sc Forum. There might be relevant details there:

https://forum.image.sc/t/how-to-save-plotservice-xyplot/70111/2