* vertx plugin impl

[Performance Improvement]Backend streaming thread model improvement

* Zookeeper plugin

* Support lettuce plugin

* lettuce plugin bugfix

* lettuce plugin fix license issue

* lettuce plugin fix cluster and config issue

* plugin lettuce compatible with low 5.0.x version

* lettuce plugin support version accurately describes on Supported-list.md

* plugin lettuce compatible with low 5.0.2 version

* lettuce plugin fix wrong batch method intercept point

* move lettuce to optional plugins

* fix ci issue

* fix ci issue

* Modify the description file

* Pom code optimization

* Optimization operation name

* Optimization operation name2

* plugin support redisson

* Support Gson plugin

* Support webflux and spring mvc 5 plugin

* Change instrumentation

* Change instrumentation

* fix check style

* Add support 2.1.x instrumentation

* 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

* Add Undertow 2.x plugin

* Undertow: Interceptor method executeRootHandler in class Connectors

* Change version number to 6.0.0-alpha-SNAPSHOT

* Enable the build of ServiceComb Java Chassis

* Updated the Supported list

Update document based on #771

Correct the English.

Remove OJDBC and resin artifacts from ci-dependencies driectory as they as not Apache license compatible.
The user can onetime manually download them, and the maven reactor will automatically build the corresponding plugins.

OJDBC is OTN which requires a user click-through agreement.
Resin is GPLv3, meaning any derivative work must also be GPLv3 licensed.
https://www.apache.org/licenses/GPL-compatibility.html

ref: https://github.com/apache/incubator-skywalking/pull/737