* Move submodule plugin.

* Always auto-submodule

* [maven-release-plugin] prepare release v6.1.0

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

* Change keys location.

* Fix #2546

* Change the stackdepth type

* Fix bug

* Fix CI failed

Update all "incubator-skywalking" to "skywalking" ,"incubator-servicecomb-java-chassis" to "servicecomb-java-chassis" correctly, and ".gitmodules" will update at #2531 (#2548)

* vertx plugin impl

Modify postgresql-8.x-plugin CreateStatementInterceptor.java statementName from CallableStatement to Statement

- found the unnecessary else block and remove it
- add test cover when AMQP.BasicProperties had null headers or headers Map had null value keys

issue #2450

* Fix npe

* support dubbo 2.7.x

* updated

* rename package

* rename package

* fix UT

* rename class

1. Fixed the warning of 'parent.relativePath' points issue when running the mvn package command. (#2404)

2. Fixed the warning of duplicate declaration of plugin issue when running the mvn package command.
3. Fixed the warning of duplicate declaration of mysql connector jar when running the mvn package command, because of provided scope include test scope.
4. Fixed the warning of expression ${artifactId} is deprecated issue when running the mvn package command.
5. Fixed the warning of expression ${version} is deprecated issue when running the mvn package command.

Update apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/context/trace/AbstractTracingSpan.java

Fix isInAsyncMode never be set.
Co-Authored-By: wu-sheng <wu.sheng@foxmail.com>

* bugfix: fix bug when spaces in agent path. resolve #1219

* fix code style

* fix code style

* fix issue #2258

* fix #2097 #1947

* remove Description and date tag

* split the diferent version to different plugins

* resolve conflict

* record all ips on multiple host mode of mysqlconnector-5x

* fix jdk 6.x

* optimise the code

* optimise code

* modify class name

* fix #2097 #1947

* i do not think it is a good idea to move the Instrumentation to mysql-common,the better way is extract a public method to return the InteceptorPionts in mysql-common

* fix #2097 #1947

* remove witnessClasses of subclasses

* Submit custom enhancement kernel code for the first time.

* Submit the code again.

* Optimize ClassUtil code.

* Submit custom enhancement plugin code for the first time.

* To fix CI issue.

* To fix CI header Tmp issue

* To fix CI Tmp header issue

* Customize plugin code submission

* Add md file.

* Fix some bug.

* Fix ci issue

* Fix md desc

* Fix unapproved license

* Fix bug

* Fix collection bug.

* Fix java8 pair ref issue

* Fix CI issue.

* Add more detail for expression.

* Fix review issue

* Fix review issue 2

* Fix review code issue 2

* Fix md issue

* Fix bug and op desc md.

* Update customize-enhance-trace.md

* Update customize-enhance-trace.md

* FIx code review issue.

* add instance id configuration item

* add doc about instance uuid

* Add peer to entry span

* Fix CI

* Fix ArrayIndexOutOfBoundsException when intercepting net.spy.memcached.MemcachedClient.getStats()

* revert format