Adds electric versions of the stone and steel furnaces, and an electric boiler. This is an update and tweak to the Electric Furnaces mod by 'GotLag', later revised by 'yukisoha'.

As 'owlpaste' pointed out (thank you.) There are no Electric Furnace 2 and 3. And some of the electricity consumption levels are different.

For the most part, I've simply updated some of the graphics, and code to be compatible with Factorio 2.0/Space Age. Thank you Wube, and Gotlag, Yukisoha.