[Changed] Net messages now have a burst instead of a fixed timer

Before, you could send 1 net message per second. End of story.

Now, it uses a "burst" instead. This means that every time you send a
net message, your counter decreases by one. When it reaches 0, you can't
send any messages. Every 0.5 seconds, all SF chips's burst amounts are
increased by one, back up to a cap of 10.