Pass configuration into functions instead of loading internally

[teneightfive]

Problem

Currently we load configuration into modules locally. This makes them hard to test and sometimes hard to follow.

An example can be seen in the discussion on #686.

Possible solution

Pass configuration into each function call separately. This will mean refactoring controllers and presenters a substantial amount but will make things easier to follow and test.

Example:

router.get('/', controller(config))

function controller(config) {
  return (req, res) => {
    const output = items.map(presenter(config))
    ...
  }
}

function presenter(config) {
  return (item) => {
    ...
  }
}