Activate foreground service only when a recording is active

[GrazianoCapelli]

Te foreground service might be active only when one of the following conditions are true:

• The user is recording Trackpoint (i.e. when the "Trackpoints" button is red);
• The user is acquiring a Placemark (i.e. when the "Placemarks" button is red);
• The current track is not empty (the amount of Trackpoints and Placemark is > 0);

Otherwise the foreground service should be closed when the app is sent in Background.