Permit Max Column for Row Breaks

[oleibman]

Fix #3143. Page break was dropped. Difference between good and bad was the use of attribute max in brk tag in the good spreadsheet. However, max was not required in a similar spreadsheet. So the reason for the problem isn't completely explained, although the likeliest explanation seems to be an Excel bug. Nevertheless, it can't really hurt to capture the max value on read (if present) and generate it on write. This resolves the issue. User is also permitted to specify max column when setting a row break programatically. Documentation is updated.

This is:

• a bugfix
• a new feature
• refactoring
• additional unit tests

Checklist:

• Changes are covered by unit tests
  • Changes are covered by existing unit tests
  • New unit tests have been added
• Code style is respected
• Commit message explains why the change is made (see https://github.com/erlang/otp/wiki/Writing-good-commit-messages)
• CHANGELOG.md contains a short summary of the change and a link to the pull request if applicable
• Documentation is updated as necessary

Why this change is needed?

Provide an explanation of why this change is needed, with links to any Issues (if appropriate).
If this is a bugfix or a new feature, and there are no existing Issues, then please also create an issue that will make it easier to track progress with this PR.

[oleibman]

I have tested further, using PhpSpreadsheet code to emulate the problem spreadsheet, and I am quite certain that the only difference between a spreadsheet which appears as expected and one which doesn't is the brk max attribute. This convinces me that Excel is acting strangely when faced with a row page break inside a defined print area. Bug? Feature? Who knows? At any rate, this result tells me that we should proceed with this PR. It does not convince me that it is always safe to add the max attribute, nor that the value should always be 16,383, but I can at least document when this should be done and suggest that as a reasonable value to use. I will update this PR with a documentation change and additional tests.

[oleibman]

BTW, LibreOffice handles the printing correctly whether or not max is specified on brk.