* [Feature] Officially support ElasticSearch 7 as backend storage
* Extract bootstrap module to be shared by multiple starters
* Add missing configuration file and distinguish different version in test
* Update known-oap-backend-dependencies-es7.txt
Update the dependency lib
* Fix missing adaptation to ElasticSearch 7
* Rename ElasticSearch 7 specific class with Es7 infix
* Fix miss-adapted ElasticSearch DAO API
* Add ES7 specific configuration and polish documentations
* Polish documentations
* Polish documentations
* [CI] Make E2E tests run in multiple JDK versions
* Polish
* Use new e2e-container version number
* Install socat in reboot case
* Fix reboot case
* Polish
* Reorganize jobs
* Override ES settings in FAQ
* Resend traffic data when invalid
* Remove unsupported ES setting
* Use seperated buffer directory and remove unnecessary web app 2