Stop using client-side validation javascript code

[pawamoy]

To avoid discrepancies between the client-side and server-side validation, we should get rid of the client-side validation using javascript. Instead, we should simply send a request upon password field modification to validate the current input against the server. The view handling the request would return the warnings and feedback. Client-side HTML page would only display the progress bar.

This would also allow validation against custom dictionaries on the client side, not only server one.

See https://github.com/pawamoy/django-zxcvbn-password/pull/95#issuecomment-566068735