Before, in order to display a toast notification, the component needed
direct access to NotificationPresenterWidget.
With this patch this restriction has been removed. The notification
handler registers itself in the Frontend which allows public access.

Add a new sub-tab under Administration -> Users -> {user} that allows
viewing user settings. The settings are displayed unformated as JSON
or plain text depending on the property type. Only remove operation is
supported.

Main use case is troubleshooting problems related to user settings.
With the new view, the admin is able to restore the default
configuration by removing incorrect user properties.