Bugfix: Files opened by fopen need to be closed again. Added check for NULL pointers after fopen.

Background: An application can only open a limited number of files in parallel with fopen. If one
never closes these handles, fopen will fail after a certain amount of open files.
Merge branch 'master' of ssh://github.com/adiesner/GarminPlugin
Now using case insensitive search for file Garmin/GarminDevice.xml
Updated version number to 0.3.17