Memory Leak in Sample35

[oleibman]

All but 6 chart samples can be rendered by Sample35. Of those 6, 3 of the problems are because the script runs out of memory processing them. Adopting a suggestion from @MAKS-dev in issue #2092, adding a call to gc_collect_cycles after the charts from each spreadsheet is rendered appears to make it possible to include those 3 spreadsheets in Sample35 after all.

PR now includes a fix for the 2 Pie 3D charts. There is now only one unsupported, and the reasons for that are documented in the code.

Also take advantage of this opportunity to correct a number (hopefully all) of Scrutinizer problems with JpgraphRendererBases.

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.