Create openambit2gpx.py

simple python script that converts the *.log xml files produced by openambit to gpx format. removes the need to go via movescount website. requires xml.etree.ElementTree, math and sys libraries. tested with python2.7.8 and 3.4.0 on an ubuntu 14.04 machine.
Merge pull request #50 from gitMarcH/patch-1

Create openambit2gpx.py