Garmin FIT file support

[andzs]

Please add FIT file support in addition to GPX file format for track upload. This JS lib could help implementation https://github.com/pierremtb/easy-fit
Suunto lately moved from Movescount service to Suunto App only. That only supports FIT file export. User must dance with some external or online conversion tools like GPSBabel to get usable GPX file format. It is worth mentioning that if automatic upload from Sunnto App service to some external service (like Strava) is used then data in derivd GPX file from that service is somehow manipulated and GPS route animation in RG2 is jerky - in playback runner makes phantom stops.