There a currently 248 occurrences of external call of the _dao attribute.
The attribute's name suggest a private one, but on the contrary, it is the most publicly used.
So, the clean-up goal is:
- Rename Engine._dao to Engine.dao, and remove Engine.get_dao().
- Rename Manager._dao to Manager.dao, and remove Manager.get_dao().
- Rename Remote._dao to Remote.dao
- Rename EngineWorker._dao to EngineWorker.dao