Switch user profile to fullName/shortName

Migrates user profiles from:

```javascript
{
  "firstName": "Mary",
  "lastName": "Smith"
}
```

to:

```javascript
{
  "fullName": "Mary Smith",
  "shortName": "Mary"
}
```

Does basically two things:

- On login, if user is on "old" data model, performs the migration and saves back to API in the background
- When fetching other patient's profiles, performs the migration when necessary so name displays correctly

So this change is backwards-compatible with any account created prior.

Closes #60