Use the new hierarchical options feature of the option parser to turn camera-related option (--capture, --file, --stream, --strict-formats and --metadata) into children of the --camera option. As an added bonus, we don't need to check anymore if a camera has been specified when capture is requested, as that's now enforced by the option parser. This change prepares for support of multiple cameras. Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>