Support Get Value by Properties or Attributes

[oldcai]

**Support get value by properties or attributes.
Not only data from fields can be rendered to chart.
With it, JSONFields could be loaded by adding a getattr function to model and handle the attribute fetching by reading from JSONField.
**

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Before submitting a PR make sure the following are checked:

• The PR relates to only one subject with a clear title and description.
• Wrote good commit messages.
• Used the same coding conventions as the rest of the project.
• Feature branch is up-to-date with master (if not - rebase it)
• Squashed related commits together.
• Reviewed the diff manually for unexpected or unrelated changes.
• Updated README.rst with change log.
• Tested changes manually.
• Added automated tests.
• make coverage tests are passing.

[atodorov]

Can you add an example chart in the demo application for this use case ?

[atodorov]

And please fix all failing tests when making changes. Thanks.