[0.85] manage on_change param for dropdowns


git-svn-id: https://forge.indepnet.net/svn/glpi/branches/0.85-work@20606 35612d4c-9d10-0410-837c-bf9dd1be60d7
[0.85] create standard function for ajax dropdown


git-svn-id: https://forge.indepnet.net/svn/glpi/branches/0.85-work@20607 35612d4c-9d10-0410-837c-bf9dd1be60d7