Xlsx Reader/Writer Composite Charts

[oleibman]

Fix #2333. Thanks to @SSI-johnnypops for discovering the problem and formulating most of the solution. The classes involved in setting up composite charts made it relatively easy to code them; however, there can be problems when reading a spreadsheet with such a chart and then saving a copy of it. In particular, the ordering conventions when reading the chart may not match the expectations when writing. The original attempt to resolve this worked for read/write but broke one of our samples (33_Chart_create_composite), which probably means that it would break other code which is now working in the wild. It has now been refined so that it (hopefully) makes adjustments to the ordering if and only if they are required. The new code works with the failing spreadsheet reported in the issue, with the unchanged sample code, and with an alternate version of the sample which contains what is probably a better model for people to use when coding such a chart.

This is:

- [x] a bugfix
- [ ] a new feature
- [ ] refactoring
- [ ] additional unit tests

Checklist:

• Changes are covered by samples
  • Changes are covered by existing sample
  • New sample has 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
• 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.