simplify roles organization and renames

molecule/default/tests/test_mediaimport.py

molecule/default/tests/test_mediaserver.py

molecule/default/tests/test_mediavault.py

molecule/default/tests/test_mediaworker.py

molecule/default/tests/test_mirismanager.py

molecule/default/tests/test_msmonitor.py

molecule/default/tests/test_netcapture.py

molecule/default/tests/test_nginx.py

molecule/default/tests/test_ntp.py

molecule/default/tests/test_postfix.py

molecule/default/tests/test_postgres.py

molecule/default/tests/test_python3.py

packer/example.json

playbooks/bench-server.yml

playbooks/bench-worker.yml

playbooks/celerity.yml

playbooks/cluster.yml

playbooks/import.yml

playbooks/includes/base.yml

playbooks/includes/celerity.yml