Fix Chart Problems and Memory Leak in Xlsx Writer

[oleibman]

This was supposed to be mopping up some longstanding chart issues. But one of the sample files exposed a memory leak in Xlsx Writer, unrelated to charts. Since that is my best sample file for this problem, I would like to fix both problems at the same time.

Xlsx Writer for Worksheets calls getRowDimension for all rows on the sheet. As it happens, the sample file had data in the last rows after a huge gap of rows without any data. It correctly did not write anything for the unused rows. However, the call to getRowDimension actually creates a new RowDimension object if it doesn't already exist, and so it wound up creating over a million totally unneeded objects. This caused it to run out of memory when I tried to make a copy of the 8K input file. The logic is changed to call getRowDimension if and only if (there is data in the row or the RowDimension object already exists). It still has to loop through a million rows, but it no longer allocates the unneeded storage.

As for the Chart problems - fix #1797. This is where the file that caused the memory leak originated. Many of its problems were already resolved by the earlier large set of changes to Charts. However, there were a few new properties that needed to be added to Layout to make things complete - numberFormat code and source-linked, and dLblPos (position for labels); and autoTitleDeleted needs to be added to Charts.

Also fix #2077, by allowing the format to be specified in the Layout rather than the DataSeriesValues constructor.

This is:

- [x] 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
• 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.