Send changesignals for placed receptors when not powered, make on_placenode code more readable

with comments. Also fixes a bug of lua- / microcontrollers not being updated when pushed by a
piston.
This could cause some bugs, even though I haven't found any while testing as it is a very core part of mesecons.

mesecons/init.lua

@@ -39,7 +39,6 @@
 --	}
 --}
 
-
 -- PUBLIC VARIABLES
 mesecon={} -- contains all functions and all global variables
 mesecon.queue={} -- contains the ActionQueue

mesecons/services.lua

@@ -1,20 +1,32 @@
 mesecon.on_placenode = function (pos, node)
+	-- Receptors: Send on signal when active
 	if mesecon:is_receptor_on(node.name) then
 		mesecon:receptor_on(pos, mesecon:receptor_get_rules(node))
-	elseif mesecon:is_powered(pos) then
+	end
+
+	-- Conductors: Send turnon signal when powered or replace by respective offstate conductor
+	-- if placed conductor is an onstate one
 	if mesecon:is_conductor(node.name) then
-			-- receptor_on if itself is powered already
+		if mesecon:is_powered(pos) then
+			-- also call receptor_on if itself is powered already, so that neighboring
+			-- conductors will be activated (when pushing an on-conductor with a piston)
 			mesecon:turnon (pos)
 			mesecon:receptor_on (pos, mesecon:conductor_get_rules(node))
-		else
+		elseif mesecon:is_conductor_off(node.name) then
+			minetest.swap_node(pos, {name = mesecon:get_conductor_off(node)})
+		end
+	end
+
+	-- Effectors: Send changesignal and activate or deactivate
+	if mesecon:is_effector(node.name) then
+		if mesecon:is_powered(pos) then
 			mesecon:changesignal(pos, node, mesecon:effector_get_rules(node), "on", 1)
 			mesecon:activate(pos, node, nil, 1)
-		end
+		else
-	elseif mesecon:is_conductor_on(node) then
+			mesecon:changesignal(pos, node, mesecon:effector_get_rules(node), "off", 1)
-		minetest.swap_node(pos, {name = mesecon:get_conductor_off(node)})
-	elseif mesecon:is_effector_on (node.name) then
 			mesecon:deactivate(pos, node, nil, 1)
 		end
+	end
 end
 
 mesecon.on_dignode = function (pos, node)