tests: In test-publish-async-ndnx, onRegisterFailed needs to be a member of Echo.
Face: Added nfdRegisterPrefix to support registering with NFD. Updated RegisterResponseClosure to try NDNx if NFD registration fails.
tests/node: Added test-publish-async.nfd.
ndn.js: Rebuild after adding support for NFD registerPrefix.
CHANGELOG: support NFD for registerPrefix.