Fix route handler property to follow same pattern

[rvsiyad]

DEFRA/water-abstraction-team#122

We have noticed that in some of our routes, the handler is within the options property.

{
  method: 'POST',
  path: '/bills/{id}/remove',
  options: {
    handler: BillsController.submitRemove,
    auth: {
      access: {
        scope: ['billing']
      }
    }
  }
}

Whilst in others it is outside:

{
  method: 'GET',
  path: '/bill-runs',
  handler: BillRunsController.index,
  options: {
    auth: {
      access: {
        scope: ['billing']
      }
    }
  }
}

This is as a result of some contradiction between the Hapi API documentation having the handler within the options property, and the Hapi Tutorial giving examples with the handler outside the options property. The decision has been made to follow the API documentation.

This PR is focused on going through the routes files and ensuring the handler is within the options property.

[Cruikshanks]