Commented a few unknown recipes and added warning message

- Added a warning message from unified_inventory when it detects a recipe involving
   an unknown item. Can be activated in minetest.conf with "show_unknown_craftrecipes" setting.
 - Commented a few of our unknown craft recipes

mods/unified_inventory/api.lua

@@ -27,6 +27,9 @@ minetest.after(0.01, function()
 							if (not groupchk and not minetest.registered_items[chk])
 							  or (groupchk and not unified_inventory.get_group_item(string.gsub(chk, "group:", "")).item) then
 								unknowns = true
+								if minetest.setting_getbool("show_unknown_craftrecipes") then
+									minetest.log("error", "Recipe for item " .. recipe.output .. " contains unknown item " .. chk)
+								end
 							end
 						end