update help of "add" command, and improve code
update help of "add" command, and improve code

RouxRC/weboob,sputnick-dev/weboob,RouxRC/weboob,willprice/weboob,nojhan/weboob-devel,laurent-george/weboob,laurent-george/weboob,nojhan/weboob-devel,nojhan/weboob-devel,RouxRC/weboob,sputnick-dev/weboob,willprice/weboob,sputnick-dev/weboob,laurent-george/weboob,willprice/weboob