Allow to change PSK and local account password on the self-service portal

[julsemaan]

Is your feature request related to a problem? Please describe. When changing the password of a local user on the self-service portal, it would be interesting to allow to sync this new password with the PSK value of the person (should be configurable). This is particularily useful when using 'Create local account' with a DPSK provisioner that has dpsk_use_local_password