Ancient Savo beta 20 : iron works and bugfixes

[Erkka]

Ancient Savo beta version 20 has just been released on itch.io

I hope all the reported bugs are fixed in this version. And as a new feature there is metallurgy, which involves steps like harvesting limonite from lake bottom, using a kiln to produce charcoal, processing the limonite to get iron ingots, and finally forging those ingots to make metal tools like spear heads.