Add wand.lua translarion. Some fixes for translations:

- add missed `count` var
- fix terminology "blocks" -> "nodes" for `//outset` `//inset`
- change textdomain `worldedit` -> `worldedit_commands`
- add missed translation ("invalid usage") in `//cubeapply`

worldedit_commands/wand.lua

@@ -1,3 +1,5 @@
+local S = minetest.get_translator("worldedit_commands")
+
 local function above_or_under(placer, pointed_thing)
 	if placer:get_player_control().sneak then
 		return pointed_thing.above
@@ -9,7 +11,7 @@ end
 local punched_air_time = {}
 
 minetest.register_tool(":worldedit:wand", {
-	description = "WorldEdit Wand tool\nLeft-click to set 1st position, right-click to set 2nd",
+	description = S("WorldEdit Wand tool\nLeft-click to set 1st position, right-click to set 2nd"),
 	inventory_image = "worldedit_wand.png",
 	stack_max = 1, -- there is no need to have more than one
 	liquids_pointable = true, -- ground with only water on can be selected as well