Camera: move all image processing out of the class

[m-roberts]

• Empty out Camera object so that it is only responsible for defining frames (e.g. resolution, mode) and returning these frames
• Convert Camera's (image processing) frame handler to be a generic image stream processor (as callback):
  • Face detection
  • Movement detection
  • Line detection
• Add clear warnings about how to use camera
• Update examples - e.g. motion detection

[sync-by-unito]

➤ Mike Roberts commented:

I’m not sure that we can move it out as it is right now, as it records video internally… This needs to be specced properly.