Move table copy function out of signs lib and into init.lua, make it global.

doors_and_gates.lua

@@ -373,7 +373,7 @@ for i in ipairs(gates_list) do
 	minetest.register_node("homedecor:gate_"..gate.."_closed", def)
 
     -- this is either a terrible idea or a great one
-    def = table.copy(def)
+    def = homedecor.table_copy(def)
     def.groups.not_in_creative_inventory = 1
     def.selection_box.fixed = { 0.4, -0.5, -0.5, 0.5, 0.5, 0.5 }
     def.tiles = {