Made the default labels for the graph obviously bad so they're implemented in the json.
Add in concept of a `column-graph` to markup

- Adds in a modifier to a `single-decker-graph`, the only change this makes a the moment is to add extra height to the graph, but could be useful for future modifications
- The SCSS is very nested, this is a shame, but probably shouldn't be tackled here
Merge pull request #819 from alphagov/feature/column-module

Feature/column module