Add "destination" values to audio coach from guiding/navigation

To make audio coach useful in real life instead of just "running around in circles" (aka training), it needs to speak about the DESTINATION as well:

"6.5 kilometers, plus 430 meters, minus 60 meters to go."

Where does the data come from?

(1) If you have set a guiding arrow to somewhere, it can simply calculate destination minus current position, basically the same values that are displayed besides the guiding arrow.

(2) If you have an active navigation or are following a track, calculating total climbing/descending value to destination is a little more complex... but still not rocket science.

I almost always use (1), so the simple case would already help a great deal. But for completeness, (2) should be addressed as well.

In any case, when on a real trip instead of just training, hearing about what you STILL HAVE TO DO as opposed to WHAT YOU HAVE ALREADY DONE is incredibly more useful.