In the "advanced settings" dialog, if "X" instead of
"apply settings" is clicked, it is seen as "cancel" and
no settings are applied.
If there do are saved settings, make sure to ask the
user on pressing "write" if they do want the saved settings
applied, instead of applying no settings.
Implemented as "validator" which will cause that if an user
presses a key that is not allowed, it will not register.
Saves having to add an error message that would need to be
translated to different languages.
Closes#474
