adding hr,cad,power,temp of Suunto Ambit gpx files

Added support for the Suunto Ambit .gpx Datafiles, 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.