Added P2P tunnel part for OpenComputers.

As discussed with @FireBall1725 on IRC, here's a PR adding a P2P tunnel part for OpenComputers networking.

Tested with and without OC, in dev-env and normal MC via vanilla launcher.

One thing that need specific review are the adjusted enums. I believe the ones where I did not append the entry to the end to be order irrelevant, but verification of that is needed.
Done.