Optionally provide serialized files in addition to CDF data in JSON exports

[saltednut]

We have basically our own custom json schema to work with here. Part of it is storing the entities key that is fed into content hub. However, we could also provide a files key that stored information about files including data serialization of images. Potentially, we could ship both raw files AND entities as "content packs" stored in json. Depending on the number of files, they could be quite big, but its worth looking into even if the json files balloon from 2mb to 50mb, given the current tarballs we ship are near 300mb.