[Feature] Add speed indication

[kimonmeier]

Description

While driving it's possible that the speedometer of the train stops working. While this is a tricky situation we're still allowed to drive the train with a maximum speed of 120 km/h. When the speedometer stopps working you're already in an stressfull situation, the fact that you've to manually calculate your speed in your head makes it much worse. To prevent an overlad there should be an option to display your current speed calculated with the gps coordinates in mind.

Things to keep in Mind

• Loss of gps connection
• Inaccurate gps positions

Needed

The following issues are needed to go further: