Pressure plates and the object detector will send power to vertical

wires 2 nodes below them, allows to hide circuitry powered by them.
Fixes #179
Rewrite pressure plates + vertical wires using mesecon.register_node.

mesecons/init.lua

@@ -47,15 +47,14 @@ mesecon.queue.funcs={} -- contains all ActionQueue functions
 -- Settings
 dofile(minetest.get_modpath("mesecons").."/settings.lua")
 
--- Presets (eg default rules)
-dofile(minetest.get_modpath("mesecons").."/presets.lua");
-
-
 -- Utilities like comparing positions,
 -- adding positions and rules,
 -- mostly things that make the source look cleaner
 dofile(minetest.get_modpath("mesecons").."/util.lua");
 
+-- Presets (eg default rules)
+dofile(minetest.get_modpath("mesecons").."/presets.lua");
+
 -- The ActionQueue
 -- Saves all the actions that have to be execute in the future
 dofile(minetest.get_modpath("mesecons").."/actionqueue.lua");

mesecons/presets.lua

@@ -15,6 +15,9 @@ mesecon.rules.default =
  {x=0,  y=1,  z=-1},
  {x=0,  y=-1, z=-1}}
 
+mesecon.rules.pplate = {{x=0, y=-2, z=0}}
+mesecon.mergetable(mesecon.rules.default, mesecon.rules.pplate)
+
 mesecon.rules.buttonlike =
 {{x = 1,  y = 0, z = 0},
  {x = 1,  y = 1, z = 0},

mesecons/util.lua

@@ -199,6 +199,9 @@ mesecon.mergetable = function(source, dest)
 	for k, v in pairs(source) do
 		dest[k] = dest[k] or v
 	end
+	for i, v in ipairs(source) do
+		dest[i] = dest[i] or v
+	end
 end
 
 mesecon.register_node = function(name, spec_common, spec_off, spec_on)