VPN/RPC state changes should send the user a notification

[deansheather]

Currently we don't have a good system for notifying the user when errors happen.

• Every error should result in a Windows notification.
• Every error when starting/stopping the VPN should show red text on the tray window
• Every login error should show red text in the login window

The stack trace (if applicable) should be easily reachable but shouldn't clog up the screen.

If the VPN or RPC lifecycle state changes without user interaction then we should send a notification to the user informing them of such.