update displayed minutes until arrival every 5 seconds and while offline

Currently when viewing arrivals the minutes until arrival are only updated whenever the data is refreshed (every 30 seconds when online) or when the view is reopened (such as when a lock and unlock occurs). This PR changes the code to update the minutes until arrival every 5 seconds based on the last data received. This PR does not change how often data is retrieved from OBA servers, just how often the minutes are recalculated. This will allow the application to display more accurate arrival times while online and allow a user to see arrival times while in the tunnel as long as they open the stop view before entering the tunnel.