* Provide consul cluster plugin.

* Change log and application config file.

* Add consul's config item into the docker's application.yml.

* Fixed bug.

* Add consul description into  readme.

* Add okhttp component license.

* Support webflux and spring mvc 5 plugin

* Change instrumentation

* Change instrumentation

* fix check style

* Add support 2.1.x instrumentation

* Move oal tool back into main repo, and fix compile issue.

* Fix two bugs.

* Remove all generated codes.

* Make all oal generated codes out of source control.

* Make mvn compile and package work.

* Fix test cases.

* Make compile right and provide new documents.

* Remove an unnecessary tokens file.

2. Zookeeper implementation of the cluster module using name space to support using same zookeeper cluster by different OAP clusters.

* Support alarm in service instance and endpoint.

* Fix alarm default settings and document.

* Fix wrong default setting

* Make service instance and endpoint scopes available in alarm core.

* Fix alarm bug.

* Update document and user wall.

* Change format.

* user wall updated.

* Fix typo

* Correct namespace description

* Support sampling trace at server side and keep metric right.

* Add a trace sampling document

* Fix wrong default value.

* Fix document issue.

* Fix assemble issue.

* Fix wrong settings and doc.

* add TiDB configuration description.

* add tested mysql client driver version

Also fixed several bugs in this merge.

Notice of the system time setting.

* feat:Active System.env Config In Both Collector And agent.config.
1、moving related codes into apm-util module.
2、update Setting-override.md about how to use.

* resolve docs.

* typo

* finish test case.

* Update README.md

* support set config from system.envs.

* 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.

* Change some codes to make zipkin receiver works, not done yet.

* @adriancole Zipkin receiver is coming back again.

* Fix document and fix for Zipkin receiver.

* Fix some bugs.

* Fix register bug.

* Fix transfer bug for new backend core.

Fix typo

* ZooKeeper Version Compatibility

* Update backend-cluster.md

Reorganize words. cc @peng-yongsheng

* Update application.yml

* Update application.yml

* Support for overriding config with agent options

* Test the separator of options

* support quotes in agent options

* revert imports change

* add more tests

* clear properties after each test

* add document

* fix code style

* Add Rocketbot ui

* update set-up

* Lock oracle and resin plugins version.

* Move resin and oracle plugin to openskywalking

* Restore submodule active.

* Add another submodule active command.

* Remove the wrong test cases in release and fix some doc issues.

* [maven-release-plugin] prepare release v6.0.0-alpha

* [maven-release-plugin] prepare for next development iteration

* Fix some doc

grammar fix

* Avoid service inventory object concurrency situation.

* Fix concurrency for minute persistence and others

* Fix document todo.

* Update license. Fix package with dirty agent plugin jar files.

* Fixed not combine error in persistence register worker.

* Update submodule skywalking-ui

* Add kubernetes and istio setup documents

* Remove kubernetes scripts

* Add more documents for v6.

* Make default setting consistent .

2. Make service relation and endpoint relation to record component id.
3. Delete service mapping indicator.
4. Make service inventory to record mapping service id.
5. Refactor global topology query and service topology query.

* Replace v5 changes by a link to 5.x branch. New v6 changelog.

* Finish query doc and fix a missing field in alarm doc.

* Add link to official oal in alarm doc.

* Fix words.

* Fix some doc

* Update README.md

* Update README.md

* Update README.md

* Update README.md

* Fix broken links to the correct page.

* Direct getting started links to the correct doc

* Add Undertow 2.x plugin

* Undertow: Interceptor method executeRootHandler in class Connectors

* Change version number to 6.0.0-alpha-SNAPSHOT

* Support alarm message.

* Fix document words.

* Support alarm hook.

* Fix javadoc issue.

* Sync submodule

* Sync submodule

* New generated indicators for real backend system.

* Support cpm and new indicators.

* Fix CI and change document.

* Remove an useless line.

* Change oal doc.

* Remove typo

* Remove document WIP tag.

* Fix few words.

* no message

* Adjust contribution guides.