Updated French resource and readme.txt

git-svn-id: http://plugins.svn.wordpress.org/thin-out-revisions/trunk@830933 b8457f37-d9ea-0310-8a92-e5e31aec5664
language resource update

- updated French resource
- Japanese description added

git-svn-id: http://plugins.svn.wordpress.org/thin-out-revisions/trunk@836045 b8457f37-d9ea-0310-8a92-e5e31aec5664