add application/gpx to accepted MIME types (fix #10309)
add application/gpx to accepted MIME types (fix #10309)

tobiasge/cgeo,cgeo/cgeo,tobiasge/cgeo,tobiasge/cgeo,matej116/cgeo,cgeo/cgeo,matej116/cgeo,rsudev/c-geo-opensource,rsudev/c-geo-opensource,cgeo/cgeo,cgeo/cgeo,rsudev/c-geo-opensource,matej116/cgeo