Tracking issue for redesign

[willcrichton]

• Undo stack
• Bounding box labeling
• Performance issues
• Settings
• Jupyter keybindings
• Crop images
• Gender/identity (categorical) metadata on bboxes
• Labeling multiple interval sets simultaneously (e.g. conversations and scenes)
• Poses and face keypoints
• Custom block level metadata (e.g. indicate which frame is a boundary)
• On-demand non-interval metadata (e.g. video name, frame number)