Add modal for connection problem

[CommanderRedYT]

• It should only be shown the first time a device is failing to connect to. (Resets after successful connection; maybe also when different status code?)
• It should have a collapsed section with debug information
• It should show a non-technical description and maybe some solutions (if it's 503, say that it's a problem with proxy or whatever)
• Somehow show that the device is offline

[CommanderRedYT]

Idea: Where the top bar with the device selection is available, show a icon. When clicked on it, open modal with all connection info. Icon shows status of connection (online/offline).