Overlapping cells

[martinRenou]

I am reconsidering overlapping cells support. I think it can be confusing for users, I find it confusing myself, and if we remove it I see possible performance improvements.

Currently, when a cell value/metadata changes (whether it's a single cell or a cell range) we need to recompute the sheet data by looping over all the cells. This ensures that the newly added cells get precedence over the "old" ones if they are overlapping. If we drop overlapping cells support, when a cell value/metadata changes, no need to loop over all the cells. We just update the sheet data on the row/column indices of the cell.

[martinRenou]

What if a "numeric" cell overlaps with a "date" cell? What would be the expected behavior? I would expect it to crash at cell creation Python side. Something like a RuntimeError or a TypeError if that makes sense.