Add state, state abbreviation, country, and continent

[mmazanec22]

A volunteer manually altered city and added state, state abbreviation, country, and continent and gave me a CSV. I overwrote the existing city field and added the others via script. I also manually deleted the COVID-19 category, since we didn't really end up using that anyway.

[tdooner]

Great, thanks. As we discussed in Slack here is a checklist to get this merged:

• [x] Leave "city" field untouched. You can mark it "DEPRECATED" in the README.md given the following changes
• [x] Add a "location" object which includes keys for "city", "state" (the abbreviation or full name - you choose), and "country"/"continent" if you really want it. It would be great if we could backfill this object for all existing brigades but I don't think that's necessary. We could make it a non-required field to begin with.
• [x] Add documentation to the README of the format of the "location" sub-object
• [ ] (Optional) Add JSON-schema validation for the "location" object.

[mmazanec22]

@tdooner if we're adding a location object, would it make sense to move the coordinates there too and deprecate the lat and lon living on the parent object?

[tdooner]

Looks great, thanks! I think I took care of the merge conflicts.