Added P2P tunnel part for OpenComputers. #579
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 needs 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.
I would consider the API and localization currently under lockdown until it is finally merged. Otherwise it just makes things more complicated.
The code style does not look like it is matching our.