the noise over tcp blueprint had two unresolved questions:
* what do we do for IPv6?
* what do we do for UDP support?
this change punts those two questions for later and explicitly
rejects solving them as part of noise over TCP for now.
this change also punts renaming NodeURL to reduce codebase
churn.
Change-Id: Ib209942bae61716b2ff6cea852c336af072d8bc5