Feature: use Firebase authentication and authorization

[davidpelfree]

For data security reasons, need to get user ID and credentials per user.
This should be managed in Firebase. See API here: https://firebase.google.com/docs/auth

The benefit is that you can then limit the data visibility per user / role by using "database rules". See: https://firebase.google.com/docs/database/security

[davidpelfree]

Duplication of #134?