Refactor complex methods

[NoB0]

The following methods are too complex and need to be refactored:

• [ ] NLG.generate_output NLG._clarify_CIN
• [ ] NLG._user_options_remove_preference
• [ ] NLG._user_options_remove_preference_CIN
• [ ] UserIntentsChecker._filter_dact
• [x] DataLoader.load_database
• [ ] NLU.generate_dact
• [x] RBAnnotator._year_annotator
• [x] DialoguePolicy.next_action
• [ ] DialogueStateTracker.update_state_user
• [x] Agent.initialize

[kbalog]

The remaining ones will be part of v2 (a new issue is to be created for them).

[IKostric]

I have created a new issue for the remaining complex methods.