[UNSTABLE] AkkaProtocolManager, ThreadLocalRandom, more

Made some fixes to the `AbstractTransportAdapters` and implemented the `AkkaProtocolManager` in its entirety.

Also imported a `TheadLocalRandom` implementation from my personal Akka implementation (but it's really Jon Skeet's design anyway.) Currently using that inside `ActorSystem` to seed Uids for rebooted transports.