multi-squares in multi-squares in ...

Did this a while ago, but wanted to find a neater solution. Didn't find one and forgot to do it so ill just PR it now if you want to use it.

I did:

161 But only when the multi-square gets used (brush and rule update) so i could have missed cases. Did it that way because i don't like the way it looks.
Made multi-squares in multi-squares work with brush and rules on left and right side. This fixes: #163 / #215 and kind of #322 (only fixes that that setup doesn't error in the rule update and not what it does when it errors)

Stuff i am not happy with/ is janky:

The merge instruction merges m∗n cells. When i want to merge this: ⊞⊟ it isn't m∗n. Because the merge instruction is inplemented by merging next m∗n cells, i just tell it to merge n∗1 cells (6∗1 in the case of ⊞⊟).
I implemented almost the same thing three times.
- flattenAndFillDiagramCells it flattens nested cells and fills the voids.
- addDiagramCellsToLeftList it does the same but for rule gen on the left side. Also it returns what structure the nested cell had.
- addDiagramCellsToRightList it does the same but for rule gen on the right side and it uses the structure to tell when merge/split
Because the rule update needs nested cells, multi-cells have to be flattened every time they get used else where (in the splitCellToDiagram function).

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TodePond / CellPond