ExtraModMod concepts

The Fall from Heaven 2 concepts page should be renamed to ExtraModMod concepts. It should get a page for multiple production (Denev's readme). It could also get pages for AIAutoPlay and Advanced Diplomacy (Caveman 2 Cosmos). I should also review new ExtraModMod features and add any missing concepts.

Having the BtS concepts category on civilopedia serves no purpose. It will be hidden.