0.10.0b2

Fixed

• A restore cut off at the wrong moment could lose the database: if the app stopped while a
  backup was being restored, its next start could remove the database instead of putting it back.
  The database is now always moved first, and one that was never moved is left alone.
• A backup from a newer version that adds a setting to a sensor (a new reading mode, say) is now
  refused with the sensor's name, like a sensor export from a newer version, instead of being
  restored into an app that does not know the setting.
• Only the AI models VisionState itself downloads come back from a backup, and only unchanged.
• Restoring a sensor export, or importing a backup as a sensor, now says where the file goes.