yi-jing: morphogenesis using Yi Jing trigrams

The eight Yi Jing trigrams are replaced by black and white disks, which are placed on a grid.
A set of rule is applied to fill the missing cells of the grid, and to extrapolate to bigger grids.

A good set of rules is:
- complementarity by central symetry
- connect similar colors on each circle
- add new sets of trigrams, and progressively rotate each new set clockwise
- finally a last arbitrary rule to solve the remaining cases is necessary
