Feature-complete API v2 model layer refactor

DONE: Remove CoreData
DONE: Replace CoreData models with JSONModel models
DONE: Refactor ViewController logic to match API v2 workflow
DONE: Replace Civic API v1 -> v2
DONE: Test partisan party picker w/ real data

TODO: Test election picker w/ real data (ok in test with sample data)
      Unable to at the moment due to no valid elections with multiple
      elections

Items done as cleanup:
  - Comment out test election
  - Properly format Election API dates
  - Set remaining model properties to Optional
  - Make election container view transparent
  - Add state name to state details list
  - Bugfix/cleanup home view update logic
Fix existing tests, remove outdated tests
Update README and settings.plist template