Add user management about hedy

[fpereiro]

1. Set up redis.

2. Set up user account routes:

POST /auth/signup
- age (optional)
- gender (optional)
- country (optional)
- email
- password
- username (unique)
- set extra field in db: createdAt

POST /auth/login
- username or email
- password
- set/update extra field in db: lastAccess

POST /auth/logout

POST /auth/recover
- username or email

POST /auth/reset
- token
- password

POST /auth/changePassword
- oldPassword
- newPassword

POST /auth/updateProfile
- age (optional)
- age (optional)
- gender (optional)
- email (optional)
- password

GET /users (admin only through hardcoded whitelist in server)

3. Lightweight admin: list, perhaps pagination.

[fpereiro]

Deployed to master :)