Implement new UI
Follow instructions from Design team to implement the new UI: https://gitlab.gnome.org/Teams/Design/app-mockups/blob/master/notes/notes-aday.png
Based on those mockups, we can list the following tasks:
- #136 (closed) Implement the list row pattern in main view;
- Implement the list row pattern in tags (notebooks) view;
- Implement the list row pattern in settings view (or remove it);
- Implement context menu in main view;
- Implement start window;
- #154 Implement the adaptive sidebar design;