prepare change notif


git-svn-id: https://forge.indepnet.net/svn/glpi/trunk@21888 35612d4c-9d10-0410-837c-bf9dd1be60d7
begin working on change notif see #1330


git-svn-id: https://forge.indepnet.net/svn/glpi/trunk@21890 35612d4c-9d10-0410-837c-bf9dd1be60d7