Suggested new hierarchical layout: cactustree

[maartenzam]

I like those and I think they can work well for some hierarchical data
https://creativecoding.soe.ucsc.edu/pdfs/Dang_CactusTree_PacificVis_2017.pdf
https://cactustrees.github.io/

[thomasp85]

Fixed in 3b18c35