Changed Mese object to be more consistent with the idea of getting something

other than the block you originally mined when digging the stuff.  Similar to
iron, coal, etc. but as a crystal rather than an ore.

Added new textures for mese in stone, mese crystal, mese ingot, and mese block.
Block uses a variant of the old black-on-yellow mese texture.

Made the mese in stone drop a single mese crystal when mined.  Smelt one of
these crystals into a mese ingot (same cook time as iron lump -> steel ingot).

Changed the mese pick recipe in default to use the above "default:mese_ingot"
instead.

Changed the mese-as-a-fuel recipe to use "default:mese_crystal".

Added recipe to craft mese block ("default:meseblock") from 9 mese ingots, and
to craft it back to same.

Added recipe to craft mese-in-stone out of one mese lump and one block of stone
for backward compatibility with old mods that depended on the original mese
object.

mods/default/init.lua

@@ -259,7 +259,7 @@ minetest.register_craft({
 minetest.register_craft({
 	output = 'default:pick_mese',
 	recipe = {
-		{'default:mese', 'default:mese', 'default:mese'},
+		{'default:mese_ingot', 'default:mese_ingot', 'default:mese_ingot'},
 		{'', 'default:stick', ''},
 		{'', 'default:stick', ''},
 	}
@@ -470,6 +470,32 @@ minetest.register_craft({
 	}
 })
 
+minetest.register_craft({
+	output = 'default:meseblock',
+	recipe = {
+		{'default:mese_ingot', 'default:mese_ingot', 'default:mese_ingot'},
+		{'default:mese_ingot', 'default:mese_ingot', 'default:mese_ingot'},
+		{'default:mese_ingot', 'default:mese_ingot', 'default:mese_ingot'},
+	}
+})
+
+minetest.register_craft({
+	output = 'default:mese_ingot 9',
+	recipe = {
+		{'default:meseblock'},
+	}
+})
+
+minetest.register_craft({
+	type = "shapeless",
+	output = 'default:mese',
+	recipe = {
+		'default:mese_crystal',
+		'default:stone',
+	}
+})
+
+
 --
 -- Crafting (tool repair)
 --
@@ -500,6 +526,12 @@ minetest.register_craft({
 	recipe = "default:iron_lump",
 })
 
+minetest.register_craft({
+	type = "cooking",
+	output = "default:mese_ingot",
+	recipe = "default:mese_crystal"
+})
+
 minetest.register_craft({
 	type = "cooking",
 	output = "default:clay_brick",
@@ -566,7 +598,7 @@ minetest.register_craft({
 
 minetest.register_craft({
 	type = "fuel",
-	recipe = "default:mese",
+	recipe = "default:mese_crystal",
 	burntime = 30,
 })
 
@@ -745,6 +777,15 @@ minetest.register_node("default:stone_with_iron", {
 	sounds = default.node_sound_stone_defaults(),
 })
 
+minetest.register_node("default:mese", {
+	description = "Mese Crystals in Stone",
+	tiles = {"default_stone.png^default_mese.png"},
+	is_ground_content = true,
+	groups = {cracky=1},
+	drop = "default:mese_crystal",
+	sounds = default.node_sound_defaults(),
+})
+
 minetest.register_node("default:dirt_with_grass", {
 	description = "Dirt with Grass",
 	tiles = {"default_grass.png", "default_dirt.png", "default_dirt.png^default_grass_side.png"},
@@ -990,14 +1031,6 @@ minetest.register_node("default:wood", {
 	sounds = default.node_sound_wood_defaults(),
 })
 
-minetest.register_node("default:mese", {
-	description = "Mese",
-	tiles = {"default_mese.png"},
-	is_ground_content = true,
-	groups = {cracky=1},
-	sounds = default.node_sound_defaults(),
-})
-
 minetest.register_node("default:cloud", {
 	description = "Cloud",
 	tiles = {"default_cloud.png"},
@@ -1515,6 +1548,14 @@ minetest.register_node("default:steelblock", {
 	sounds = default.node_sound_stone_defaults(),
 })
 
+minetest.register_node("default:meseblock", {
+	description = "Mese Block",
+	tiles = {"default_mese_block.png"},
+	is_ground_content = true,
+	groups = {cracky=1},
+	sounds = default.node_sound_defaults(),
+})
+
 minetest.register_node("default:nyancat", {
 	description = "Nyan Cat",
 	tiles = {"default_nc_side.png", "default_nc_side.png", "default_nc_side.png",
@@ -1613,6 +1654,11 @@ minetest.register_craftitem("default:iron_lump", {
 	inventory_image = "default_iron_lump.png",
 })
 
+minetest.register_craftitem("default:mese_crystal", {
+	description = "Mese Crystal",
+	inventory_image = "default_mese_crystal.png",
+})
+
 minetest.register_craftitem("default:clay_lump", {
 	description = "Clay Lump",
 	inventory_image = "default_clay_lump.png",
@@ -1623,6 +1669,11 @@ minetest.register_craftitem("default:steel_ingot", {
 	inventory_image = "default_steel_ingot.png",
 })
 
+minetest.register_craftitem("default:mese_ingot", {
+	description = "Mese Ingot",
+	inventory_image = "default_mese_ingot.png",
+})
+
 minetest.register_craftitem("default:clay_brick", {
 	description = "Clay Brick",
 	inventory_image = "default_steel_ingot.png",