Recent history of vehicle ping results

Besides the usual individual vehicle ping results pushed via async notifications, as of TethysDash 4.99.48 a new API endpoint returns a short recent history of such results.

Dash4 4.98.9 exercises this new endpoint to provide a basic history display.

When the tooltip or dialog associated to the cell connection status button is opened, a widget with an array of small colored icons is included, showing whether the vehicle has been reachable or not at corresponding recent times. The display is updated as new ping results arrive via the usual push notifications.