window: password edit: add opt-in confirmation-password field

window: password edit: add opt-in confirmation-password field

For when the product UI using this component wants to show an extra
confirmation field where the user that executes the password change,
have to confirm their own password.

Reported-by: Wouter Arts <security@wth-security.nl>
Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>
 [ TL: use already included CBind mixin instead of constructor ]
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>