Replaces plutonium for neptunium in Cerys.

Intended to prevent duplicate plutonium items in Bluetonium , Nuclear Fuel, or any other mod that adds plutonium. Do note that Plutonium Energy and Transplutonic already have compatibility with Cerys (even if the balance is a bit weird), and they use the same internal names for Pu-238 and 239, using this mod with one of those will make all plutonium neptunium instead!

Any suggestions and non-spanish localizations welcome.