Exclude the Highcharts dependency and provide a minimal replacement

[ahus1]

Closes #809

[ahus1]

This is an example out, all charts will be gone:

This minimal replacement will continue to provide a js/stats.json file which we can use for our reports.

See the ZIP file of a small example run here: result.zip

[ahus1]

@kami619 - I managed to remove the problematic library. The output is not so nice, but sufficient for our automatic nightly runs. I assume we would then need to rely more on the Grafana dashboards :-/

[kami619]

the changes look good to me, and thanks Alex for providing a functional replacement to high charts. I think we could live without the graphs, in the end even in the html charts, I was mostly following the numbers, which are still present.

[kami619]

@ryanemerson feel free to review this further and merge it if you are satisfied as well.

[ryanemerson]

Thanks @ahus1