Make items on ground have a shadow.

There are 4 different states for things in the world:
- Regular node in world
- Item stack on ground
- Item entity (falling)
- Falling node entity

The entity states are not interactable at all, and regular node
doesn't rotate.  We can help differentiate node-in-air vs
node-stack-on-ground with a shadow visual.

Sometimes a node will get stuck as an entity inside another node's
negative space (e.g. a nodebox) and having a way to tell that it's
not a real one should maybe help.

docs/roadmap.txt

@@ -15,8 +15,7 @@ ROADMAP (SHORT-TERM)
 	- Pick can break stone into cobble, then loose cobble.
 	- Shovel can dig solid dirt as-is.
 - Stone tech.
-	- Dig up stone, ore using pick.
-		- Converts to loose cobble / loose ore (hand-diggable, falling)
+	- Dig up ore using pick.
 		- Tin, copper, iron.
 	- Combine loose cobble onto staffs to form stone tools
 		- Level 3

mods/nc_api/node_alternate_loose.lua

@@ -1,6 +1,6 @@
 -- LUALOCALS < ---------------------------------------------------------
 local minetest, nodecore, pairs, type
-= minetest, nodecore, pairs, type
+    = minetest, nodecore, pairs, type
 -- LUALOCALS > ---------------------------------------------------------
 
 --[[

mods/nc_items/init.lua

@@ -17,8 +17,15 @@ local function invdef(pos)
 end
 
 minetest.register_node(modname .. ":stack", {
-		drawtype = "airlike",
-		tiles = { "nc_items_matte.png" },
+		drawtype = "nodebox",
+		node_box = nodecore.fixedbox(
+			{-0.5, -0.5, -0.5, 0.5, -7/16, 0.5}
+		),
+		use_texture_alpha = true,
+		tiles = {
+			"nc_items_shadow.png",
+			"nc_items_blank.png",
+		},
 		walkable = true,
 		selection_box = stackbox,
 		collision_box = stackbox,

mods/nc_terrain/node.lua

@@ -1,6 +1,6 @@
 -- LUALOCALS < ---------------------------------------------------------
 local ipairs, minetest, pairs
-= ipairs, minetest, pairs
+    = ipairs, minetest, pairs
 -- LUALOCALS > ---------------------------------------------------------
 
 local modname = minetest.get_current_modname()

mods/nc_woodwork/tools.lua

@@ -1,6 +1,6 @@
 -- LUALOCALS < ---------------------------------------------------------
 local ItemStack, minetest, nodecore
-= ItemStack, minetest, nodecore
+    = ItemStack, minetest, nodecore
 -- LUALOCALS > ---------------------------------------------------------
 
 local modname = minetest.get_current_modname()