* Update new protocol
* Support new protocol at agent side.
* Fix test case.
* Make backend supports new trace protocol
* Fix tests.
* Make all new services available in gRPC.
* Fix bugs.
* Finish new document for v2 trace protocol.
* Fix wrong version requirement of zk
* Fix trace query bug.
* Find a client side dictionary bug.
* Fix register bugs.
* Fix break doc links.