Prevent vacuum tubes breaking themselves and refactor code (#51)

also bumps `min_minetest_version` to 5.4.0

mod.conf

@@ -2,4 +2,4 @@ name = pipeworks
 description = This mod uses mesh nodes and nodeboxes to supply a complete set of 3D pipes and tubes, along with devices that work with them.
 depends = basic_materials
 optional_depends = mesecons, mesecons_mvps, digilines, signs_lib, unified_inventory, default, screwdriver, fl_mapgen, sound_api, i3, hades_core, hades_furnaces, hades_chests
-min_minetest_version = 5.2.0
+min_minetest_version = 5.4.0