[Redesign] Implement a general notification mechanism

[DocMoebiuz]

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Is your feature request related to a problem? Please describe. We want to notify the user about certain things. These might require immediate action, or they also might be less important.

Confirmations:

• General mechanism in place to show notifications in the UI
• Notifications can be displayed as toast or similar
• A notification list is available to see all notifications that were generated since starting the application

Example notifications:

• HubHop events are older than 7 days.
• A device connected, disconnected
• Simulator detected, simulator connection dropped
• Firmware update available
• Orphaned serials found