De-anonymize Account

[amiantos]

When users who are signed into iCloud install Numu, they're signed up with an anonymous account using their iCloud app key. If users would like to use their account on another platform (Android and Web some day, or if they want to use the app on a device without iCloud) they'll need to be able to assign an email address and password to their account.

This won't be necessary until cross-platform versions of the app exist.