Add setName Method for Chart

[oleibman]

Addresses a problem identified in issue #2991. Chart name is set in constructor, but there is no method to subsequently change it. This PR adds a method to do so.

This is:

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

Checklist:

• [x] Changes are covered by unit tests
  • [x] 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.