- actor class flyout tweaks
- remove unused engine pause feature
- remove unused method
- code cleanup
- EngineButtons cleanup
- cleanup
- cleanup / comment env helpers
- move new_project notify to EngineProject
- EngineSliders cleanup
- remove env[:last_message_bus_activity_at]
- rename Engine#project and Engine#view to set_opengl_project, set_opengl_view