add __getitem__ on WebNip to get a loaded backend by name
add __getitem__ on WebNip to get a loaded backend by name

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