Supersedes PR #1415 by @AndrewMonty, which went stale in May 2020, and which is not directly usable due to changes between now and then. Fix#1414, which also went stale; I will remove the stale status and reopen the issue pending the merging of this PR.
Add an option to CSV Writer so that it writes the cells for a row only through the highest data column used in the row, rather than through the highest data column used in the worksheet.
oleibman