Insurance companies and onboarding fixes

Using `primary` simplifies both the server and client. Instead of having to compute the current address from a bunch of occupancies, I think it makes more sense to allow the patient to say, "yeah, that's my primary/permanent address," rather than having us try to deduce it. 

From a technical perspective, `primary` is just a boolean attribute in the occupancies table. A patient (or any other class with an address) has a `primary_occupancy`, defined as the occupancy where `primary` is `true`. And the `address` is simply the address associated with the `primary_occupancy`.