Display reason with password change failed

When there is a policy password such as REGEX against which the password is tested, trying to change the password through the UI with an incorrect password is not correctly handled by UI.

We should instead:

1. should be able to define an error message to display to the end-user.

<extension point="userManager" target="org.nuxeo.ecm.platform.usermanager.UserService">
    <userManager>
        <userPasswordPattern>(?=.{9,})(?=.*[A-Z])(?=.*[a-z])(?=.*[0-9])(?=.*\p{Punct}).*</userPasswordPattern>
    </userManager>
</extension>