Upgrade mitoteam/jpgraph

[oleibman]

They have made some changes at my request, the major effect of which is that it will now work with 33_Chart_create_bar_stacked. This is a departure for them in that they have changed the functionality of jpgraph, not merely made sure that it is compatible with new Php releases.

This is:

• a bugfix
• a new feature
• refactoring
• additional unit tests
• updated software dependency

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.