Adding hr,cad,power,temp of the watch "Suunto Ambit2" Export gpx files

Added support for the Export .gpx datafile of the watch "Suunto Ambit2", where the heart rate, temperature and cadence are saved in <extensions> with the tag name "gpxdata:hr", ...
added the "gpxdata:bikepower" as well, which I hope Suunto will add it in future as well into the export gpx file.
I got the name bikepower from the download file of the moveslink application.

Exporting GPX data from http://www.movescount.com/ is currently the only way for me to have the ride data of the great watch "Suunto Ambit2" in GC.