Add UserAddress model and make VoterInfo query request

Replaces usage of the UserDefaults store for the address value with the UserAddress model stored in CoreData throughout the app.

Add making the voter info query as a method on the Elections model. Nothing is currently done with the response, but the request is made for the VIP test election when the FindElections view is loaded. This is temporary until the Election Detail view is implemented. Then, the request will be made when that view loads.

NOTE: The VIP voterInformation query only appears to want to return valid responses for addresses in Brooklyn, NY. I have been using: "185 Erasmus Street Brooklyn NY 11226 USA".

Also closes #12