Stop generating index.json files for the app data
We will use the same index.html files that we generate manually in the content repo for the time being.
While this is a more manual process, it also gives us more flexibility and should actually be conceptually easier to author.
While this mean that, for the time being, the two processes are equivalent, I am going to keep the separation that exists so that we can optimise either as we see fit in the future.