encapsulate each top-level category in its own "object" in the API response

[ryanpitts]

So for a geography profile, an API response might look something like:

{
    "geography": {
        "sumlevel": 50,
        "name": ...
        ...
    }
    "demographics": {
        "population_by_age_gender": {
            ...
        },
        ...
    },
    "economics": {
        ...
    },
    ...
}

with the actual data dicts tucked inside each relevant category object.

[iandees]

The profile endpoint seems to handle this and we're moving away from it anyway.