Update Weather Station Units on User Login, Preferences Update

[rajadain]

As of #3259, the Weather Station popup has units that respect the user's preferences:

However, when the user logs in, or if they update their preferences, the Weather Station units do not change. This is because of the chicken-and-egg situation between App which controls the layer, and User which controls the login and profile changes.

One way to resolve this is to make Settings listenable, which is proposed in #3264. Once that is complete, make the changes required to update the Weather Stations layer with the appropriate units.