Correct generator kind_detail values (new source)

[nvkelso]

• What did you see? We currently have kind: generator. And in Add new kinds for full HOT icon library support #1424 we set value to generator:method, but really that's too specific and we should do generator:source instead.
• What did you expect to see? Some kind_detail for those nuclear, solar, wind & etc. but inconsistent. A better source would be https://wiki.openstreetmap.org/wiki/Key:generator:source values onto kind_detail=*.
• What map location are you having problems with?

• nuclear: https://www.openstreetmap.org/node/2697712892#map=19/50.91379/0.96023
• wind: https://www.openstreetmap.org/node/4640594887#map=19/50.82552/0.27377
• solar: https://www.openstreetmap.org/node/3704770949#map=19/52.65649/0.68373

[nvkelso]

Verified: