Factor out chart code from getting started controller
Add axis customisation page with controller

- Add new css rule
- copy of code taken from GettingStartedController
Update working in how-to guide

Also removed how to headings, which do not seem beneficial
to the reader.
Merge pull request #276 from matthewdunsdon/web/feature/axis-customisation

Create axis customisation how to guide
updated local changes up to latest branch