Clean up

- delete 'layout.xaxis.categories' in `grouped-bar/model.json` and `stacked-bar/model.json`
- ran `$ python run.py all`
- ran `$ python publish.py test`
- ran `$ python publish.py publish`
- replace 'scl' with 'colorscale' (python-api v1.2.3)
- replace 'reversescl' with 'reversescale (" ")
- display 'titlefont' as object (" ")
- now only 2 incomplete examples /chart-types/log/matlab-semi-logy-2 and chart-types/log/matlab-log-log-line-2
'categories' is now obsolete in graph reference