Default: Vary wood burn times according to wood density

Retain definitions for node groups to support mods.
Burn time is unchanged for applewood, and increases in the order:
aspen, pine, apple, acacia, jungle which is also the order of wood
colour darkness.

mods/default/crafting.lua

@@ -780,40 +780,134 @@ minetest.register_craft({
 -- Fuels
 --
 
+-- Support use of group:tree
 minetest.register_craft({
 	type = "fuel",
 	recipe = "group:tree",
 	burntime = 30,
 })
 
+-- Burn time for all woods are in order of wood density,
+-- which is also the order of wood colour darkness:
+-- aspen, pine, apple, acacia, jungle
+
 minetest.register_craft({
 	type = "fuel",
-	recipe = "default:junglegrass",
-	burntime = 2,
+	recipe = "default:aspen_tree",
+	burntime = 22,
 })
 
 minetest.register_craft({
 	type = "fuel",
-	recipe = "group:leaves",
-	burntime = 1,
+	recipe = "default:pine_tree",
+	burntime = 26,
 })
 
 minetest.register_craft({
 	type = "fuel",
-	recipe = "default:cactus",
-	burntime = 15,
+	recipe = "default:tree",
+	burntime = 30,
 })
 
 minetest.register_craft({
 	type = "fuel",
-	recipe = "default:papyrus",
-	burntime = 1,
+	recipe = "default:acacia_tree",
+	burntime = 34,
 })
 
 minetest.register_craft({
 	type = "fuel",
-	recipe = "default:bookshelf",
-	burntime = 30,
+	recipe = "default:jungletree",
+	burntime = 38,
+})
+
+
+-- Support use of group:wood
+minetest.register_craft({
+	type = "fuel",
+	recipe = "group:wood",
+	burntime = 7,
+})
+
+minetest.register_craft({
+	type = "fuel",
+	recipe = "default:aspen_wood",
+	burntime = 5,
+})
+
+minetest.register_craft({
+	type = "fuel",
+	recipe = "default:pine_wood",
+	burntime = 6,
+})
+
+minetest.register_craft({
+	type = "fuel",
+	recipe = "default:wood",
+	burntime = 7,
+})
+
+minetest.register_craft({
+	type = "fuel",
+	recipe = "default:acacia_wood",
+	burntime = 8,
+})
+
+minetest.register_craft({
+	type = "fuel",
+	recipe = "default:junglewood",
+	burntime = 9,
+})
+
+
+-- Support use of group:sapling
+minetest.register_craft({
+	type = "fuel",
+	recipe = "group:sapling",
+	burntime = 10,
+})
+
+minetest.register_craft({
+	type = "fuel",
+	recipe = "default:aspen_sapling",
+	burntime = 8,
+})
+
+minetest.register_craft({
+	type = "fuel",
+	recipe = "default:pine_sapling",
+	burntime = 9,
+})
+
+minetest.register_craft({
+	type = "fuel",
+	recipe = "default:sapling",
+	burntime = 10,
+})
+
+minetest.register_craft({
+	type = "fuel",
+	recipe = "default:acacia_sapling",
+	burntime = 11,
+})
+
+minetest.register_craft({
+	type = "fuel",
+	recipe = "default:junglesapling",
+	burntime = 12,
+})
+
+
+minetest.register_craft({
+	type = "fuel",
+	recipe = "default:fence_aspen_wood",
+	burntime = 11,
+})
+
+minetest.register_craft({
+	type = "fuel",
+	recipe = "default:fence_pine_wood",
+	burntime = 13,
 })
 
 minetest.register_craft({
@@ -825,37 +919,50 @@ minetest.register_craft({
 minetest.register_craft({
 	type = "fuel",
 	recipe = "default:fence_acacia_wood",
-	burntime = 15,
+	burntime = 17,
 })
 
 minetest.register_craft({
 	type = "fuel",
 	recipe = "default:fence_junglewood",
-	burntime = 15,
+	burntime = 19,
 })
 
+
 minetest.register_craft({
 	type = "fuel",
-	recipe = "default:fence_pine_wood",
-	burntime = 15,
+	recipe = "default:junglegrass",
+	burntime = 2,
 })
 
 minetest.register_craft({
 	type = "fuel",
-	recipe = "default:fence_aspen_wood",
+	recipe = "group:leaves",
+	burntime = 1,
+})
+
+minetest.register_craft({
+	type = "fuel",
+	recipe = "default:cactus",
 	burntime = 15,
 })
 
 minetest.register_craft({
 	type = "fuel",
-	recipe = "default:ladder_wood",
-	burntime = 5,
+	recipe = "default:papyrus",
+	burntime = 1,
 })
 
 minetest.register_craft({
 	type = "fuel",
-	recipe = "group:wood",
-	burntime = 7,
+	recipe = "default:bookshelf",
+	burntime = 30,
+})
+
+minetest.register_craft({
+	type = "fuel",
+	recipe = "default:ladder_wood",
+	burntime = 5,
 })
 
 minetest.register_craft({
@@ -888,12 +995,6 @@ minetest.register_craft({
 	burntime = 30,
 })
 
-minetest.register_craft({
-	type = "fuel",
-	recipe = "group:sapling",
-	burntime = 10,
-})
-
 minetest.register_craft({
 	type = "fuel",
 	recipe = "default:apple",