Hardware coloring for itemstacks

Adds the possibility to colorize item stacks based on their metadata.

In the item/node definition you can specify palette (an image file)
and color (fallback color if the item has no palette or metadata).
Then you can add palette_index to the metadata.

Dropped itemstacks with different colors do not merge.

src/script/lua_api/l_object.cpp

@@ -737,7 +737,7 @@ int ObjectRef::l_set_properties(lua_State *L)
 	ObjectProperties *prop = co->accessObjectProperties();
 	if (!prop)
 		return 0;
-	read_object_properties(L, 2, prop);
+	read_object_properties(L, 2, prop, getServer(L)->idef());
 	co->notifyObjectPropertiesModified();
 	return 0;
 }