Warn admin when they try to switch modes

Create a notification on the server-side to alert users so as to avoid unwanted changes. Inform them to tell their users of the change in modes.
This warning should show up when changing the value from within the global settings as well as setup config level (booth in advanced mode and wizard). When a setting is added into a setup config, it takes the value of the global setting by default. If the value changes from the global value upon the setting being added, this warning should show up.

Reference: https://wiki.muzima.org/x/RoO-Aw