Write spreadsheet rows in parallel instead of in series

[tmilar]

Until now, rows are being written in series to:

• allow recalculation of sheet size between rows
• check of errors between each write.
• prevent collision with other writing sources ie. manual inputs

But, so far, there have been almost no errors in this process, and the sheet size re-calculation can be done in advance with some extra care (some 'lock' on the rows to be written, maybe a temporal cells paint to 'reserve' them).

It can be a good time to work on parallel writing.