Remove typed password from the error messages

Problem/Motivation

When the password fails to comply to Zxcvbn's criteria, error messages are displayed to help the user to produce a stronger password. The problem is that these messages currently contain the typed password what can be a security issue if someone else is currently looking at the screen.

Steps to reproduce

1. Install the module
2. Go to the user edit form
3. Fill the form and type "abcd" in the password and password confirm fields.
4. You can see the "abcd" password being displayed in the error messages

Proposed resolution

Alter error messages to remove the typed password.