Plugin Support

...G...... [DEV-3542] split conf unmarshal and removed plugin system options structure

Merge in AP/plugin-support from feature/DEV-3542-7.2 to release/7.2

* commit 'b889d5e5d8b5fde34bd9bf0a5a198dfd9dfed0bc':
  ...G...... [DEV-3542] fixed PR comments
  ...G...... [DEV-3542] fixed PR comments
  ...G......[DEV-3542] split conf unmarshal and removed plugin system options structure