Cascaded treemap

A modified implementation of Cascaded Treemaps. With respect to the original algorithm, this implementation has a better (in my opinion) cascading effect, which ensures no zig-zag behaviors in corners.

Unfortunately, this method introduces a very ugly layout error (visible on the bottom right corner, where an elongated rectangle is displayed as outside its parent container). A possible solution would be to reintroduce the same fix described in the paper linked above, but this would also reintroduce the zig-zag behavior in such corner cases.