fix(privacy): don't log email addresses and password hashes

[adrienjoly]

What does this PR do / solve?

A user kindly reported that in order to better protect privacy of user-identifiable data in case of data leak, we should prevent the logging of email addresses and md5 hashes.

Overview of changes

• update request.logToConsole() to scramble/anonymise values of email and md5 fields
• call the same method in appropriate places where user data is logged
• remove a useless log that contains user data

How to test this PR?

1. run the server locally with docker-compose up
2. open http://localhost:8080/login in a browser
3. type an email address and password (even fake)
4. the value of your email address and md5 should not be disclosed in the stdout logs of docker-compose up:

=== Sun, 27 Oct 2019 11:21:10 GMT POST /login (login.handleRequest) {"action":"login","email":"a*********@gmail.com","md5":"<MD5_HASH>"}
fetching user  { email: 'a*********@gmail.com' } ...