Desktop: Display station messages

[davidrg]

Would be nice if station messages appeared in the desktop client. This is probably going to require:

• [ ] Dealing with #36 Main Window Layout Bugs first
• [ ] Broadcast station message update availability via PostgreSQL Notification and weather server subscribe command
• [ ] Desktop client refreshes sysconfig when it receives this notification via the Web Data Source
• [ ] Desktop client queries out station message on postgres notification
• [ ] On new station message, display it at the top of the main window. Set a timer to auto-dismiss it if #133 is already implemented
• [ ] While we're at it - make the Web UI subscribe to these station message notifications too and display new ones without a page refresh.