Make wrench usable independently of technic

wrench/depends.txt

@@ -1,6 +1,6 @@
 default
-technic
+technic?
-technic_chests
+technic_chests?
-technic_worldgen
+technic_worldgen?
 intllib?
 

wrench/support.lua

@@ -66,6 +66,8 @@ function wrench:original_name(name)
 end
 
 function wrench:register_node(name, def)
+	if minetest.registered_nodes[name] then
 	    self.registered_nodes[name] = def
+	end
 end
 

wrench/technic.lua

@@ -323,7 +323,8 @@ for i = 1, 15 do
 	})
 end
 
-for tier, _ in pairs(technic.machines) do
+if minetest.get_modpath("technic") then
+    for tier, _ in pairs(technic.machines) do
 		local ltier = tier:lower()
 		for i = 0, 8 do
 			wrench:register_node("technic:"..ltier.."_battery_box"..i, {
@@ -337,5 +338,6 @@ for tier, _ in pairs(technic.machines) do
 					last_side_shown = INT},
 			})
 		end
+	end
 end