Highcharts license may be incompatible with Orange

When installing Orange 3.3.7, I noticed the directory `Orange/widgets/_highcharts/`. The [Highcharts JavaScript charting library is licensed under the CreativeCommons - Non Commercial 3.0](https://shop.highsoft.com/highcharts#non-com) license, and may not be compatible with the [Orange licenses](https://github.com/biolab/orange/blob/master/LICENSES), such as GNU GPL, or Free Software/Open Source licenses in general.
## Proposed solution

Deprecate the Highcharts library in favor of a JavaScript charting library with free/open source compatible licensing terms. E.g.
- [NVD3](http://nvd3.org/)
- [Plotly.js](https://plot.ly/javascript/)
- [Vega](https://vega.github.io/)
## References
### Highcharts license

Highcharts is [available under various licenses depending on the intended usage](https://github.com/highcharts/highcharts/blob/master/license.txt). This conflicts with both the Free Software and Open Source definitions.
### Free Software definition
- The freedom to run the program as you wish, for any purpose (freedom 0).
### Open Source definition
- 6. No Discrimination Against Fields of Endeavor

> The license must not restrict anyone from making use of the program in a specific field of endeavor. For example, it may not restrict the program from being used in a business, or from being used for genetic research.
>
> [Annotated Open Source Definition](https://opensource.org/osd-annotated)
### Creative Commons and GPL / other open source

At best, the following Creative Commons licenses are compatible with Copyleft / open-source licenses:
- CC Zero
- CC - by
- CC - by- SA

> On October 8, 2015 Creative Commons concluded that the CC BY-SA 4.0 is one-way compatible with the GPLv3.
>
> Wikipedia: [License compatibility](https://en.wikipedia.org/wiki/License_compatibility)
### Creative Commons license compatibility matrix