Feature request - Prevent local storage of configuration

[efficks]

We are using karma in an environment where users have a limited knowledge of the system.
The problem is when we want to change a setting in the configuration file to propagate to all user, the config is not propagated to then because they are saved in the browser local storage.

We need a way to propagate a new config that override the local storage or a way to completely disable the local storage.

Also, maybe karma could use the default and only store in local storage when an actual user change theirs settings. But I also need the feature describe above.

Linked to #5637 and #5479