* Codebase for zipkin span persistence.

* Fix missing fields in storage.

* Miss the latency field.

* Finish some tests.

* Fix wrong latency.

* Finish doc and reset application.yml

* Make the description more clear.

* add serviceInstanceId in Segment storage.

* add serviceInstanceId in query condition.

* 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.

* Add generate indicator and dispatcher about service topology but not test.

* Delete call type from service relation.