DDTeleporter Cooldown Vulnerability

[SenseiKiwi]

I was doing some testing on whether minecarts continue moving after passing through a Dimensional Door even on servers with Railcraft installed. The good news is that they do, although we could probably implement support for them better so that their speed and momentum are preserved exactly. The bad news is that I found a weakness in DD in the process.

I had two carts running in separate loops. Strangely, one of them would seem to stop at random. Instead of teleporting, it would fly through the door and derail. This issue affected both carts, but only one at a time. I eventually realized that it would happen if one cart tried to teleport soon after another cart had teleported. DD's cooldown timer was canceling the teleportation, but the door still slammed shut. Moreover, someone could intentionally impact the use of doors on a server by building a machine that constantly fires items into a door, resetting the server-wide cooldown over and over. We're going to have to deal with this without also impacting minecarts.