`Terms of Use` must be configured by ACP

`Terms of Use` now is given by the Language Pack, Admin can edit it by editing Language file `ucp_register.php` and upload the edited file to his right place, When Updating the board Admin edits of `Trems of Use` will lost if he replaces the old files by the new version files, If the default language is either than English, This is usually happened.

So `Terms of Use` must be a ACP config not a language file key, So any admin can edit it (even he has not a programing skills), It will be saved when updating the board or the language pack.