UI Map Enhancements

[n76]

Currently when accessing the map tab, you always start zoomed out and centered someplace over the Atlantic with the OSM map layer selected.

It would be nice if this could be customized, perhaps by some config.yml entries, allowing the site administrator to specify the default lat/lon, zoom level, and layer.

[Knobee]

I've noticed that there is a purge of all local settings when the user logs out, so the user's own version of "home" isn't stored across login/out sequences.

Perhaps we should implement a "this is a PUBLIC PC" checkbox (checked by default) during the login to denote sessions that should have all local settings cleaned?

There are a couple of other UI settings that I'd like to see retained across sessions (specifically LIGHT/DARK mode).