Adding stone knife to tools menu.

The stone knife might be a weapon, but it spends the majority of its time in my games for butchering animals and scraping pelts for leather. I feel that it could be added to the tools menu as well as continuing to be listed in the weapons menu, especially where leather has become much more important with the temperature mechanic now active. I still look the the primitive stone knife in the tools section before I realize it's actually in the weapon crafting menu.