* Revise e2-mgr-client to use API spec in new submodule ric-plt/e2mgr;
removed cached copy
* Silence many Sonar complaints
* Revise license statements in documentation files
* Revise e2-mgr-client to use API spec in new submodule ric-plt/e2mgr;
removed cached copy
* Silence many Sonar complaints
* Revise license statements in documentation files