Strawman JSON of a single manual page

Using this so I have some data to work with for implementing the HTML page. This JSON schema is a strawman, ie it exists to be torn apart and learnt from, it's not the final schema or even nearly the final.
Use data from some JSON

Rather than hardcoding values in the erb.
Make JSON more like the standardised JSON structure

- Move non-standard bits into "details" hash
- I've left out anything we're not currently using
Use improved JSON format

Eventually we'll want to move this out to a presenter but for now this.
Merge pull request #5 from alphagov/use-json

Use json for manuals data