R1:87207b2f4edb

Allow users to have multiple email addresses, and verify emails

Summary:
- Move email to a separate table.
- Migrate existing email to new storage.
- Allow users to add and remove email addresses.
- Allow users to verify email addresses.
- Allow users to change their primary email address.
- Convert all the registration/reset/login code to understand these changes.
- There are a few security considerations here but I think I've addressed them. Principally, it is important to never let a user…