Turned all boot messages into clean minetest.log() calls

- Turned all the 'print' calls at server's boot to 'minetest.log' in order to
   render it more clearly

mods/mesecons/mesecons/init.lua

@@ -126,7 +126,7 @@ function mesecon.receptor_off(pos, rules)
 end
 
 
-print("[OK] Mesecons")
+minetest.log("action", "[OK] Mesecons")
 
 -- Deprecated stuff
 -- To be removed in future releases