Give visual cue if login failes without a message

[tscheepers]

If a developer implements the login response without a message or incorrectly the user is not notified when it provides incorrect credentials. The login screen seems to be unresponsive.

I suggest we use the animate.css shake animation if authentication failes without a message. It should be applied to the whole screen. Furthermore form data should be retained if authentication is submitted. If authentication fails both email and password should be retained and if authentication is successful only the email should be retained.