Adds an option to update the scene's state dynamically, together with persistence and access controls.

• Define a schema for the scene's state
• Split public and private state
• Make public state editable via the setSceneState event
• Make an interface under /c to update the public state, update the QR code to link to it
• Show the current public state in that interface
• Make that interface use the correct fields automatically
• Show the actual current state in the state panel
• Persist the state to disk
• Keep persisting between deploys
• Sync state to UI (manually for now)
• Update from the controller
• Select fields in the controller, including editing options
• Types in the frame's config page
• Sanitize HTML in frame's control form

Out of scope:

• Authentication for the frame's API
• Better control UI, including logs, etc