- added image-export translation

git-svn-id: svn://svn.code.sf.net/p/gwyddion/code@16818 25697fe4-d644-49b8-9d30-be5465f2adf3
- update of french version

git-svn-id: svn://svn.code.sf.net/p/gwyddion/code@16819 25697fe4-d644-49b8-9d30-be5465f2adf3