1. Migrate to Java 11
2. Fix integration tests inside the project
3. Fix pom.xml structure (remove unused dependencies, extract lib versions to properties)
4. Fix checkstyle warnings reported at building phase
5. Fix time of project building. Currently build it takes about 20 minutes at CI!

07:52:10 [INFO] ------------------------------------------------------------------------
07:52:10 [INFO] Reactor Summary:
07:52:10 [INFO]
07:52:10 [INFO] simulator-parent ................................... SUCCESS [06:11 min]
07:52:10 [INFO] pnfsimulator ....................................... SUCCESS [08:22 min]
07:52:10 [INFO] netconfsimulator ................................... SUCCESS [03:11 min]
07:52:10 [INFO] onboarding-package ................................. SUCCESS [ 2.443 s]
07:52:10 [INFO] ------------------------------------------------------------------------
07:52:10 [INFO] BUILD SUCCESS
07:52:10 [INFO] ------------------------------------------------------------------------
07:52:10 [INFO] Total time: 18:00 min
07:52:10 [INFO] Finished at: 2020-04-10T05:52:10+00:00
07:52:10 [INFO] Final Memory: 79M/577M
07:52:10 [INFO] ------------------------------------------------------------------------