codec/mjpeg: GeoVision camera MJPEG support

[Alan Noble]

GeoVision camera MJPEG output should be supported (in addition to the Pi camera).

Note: GeoVision cameras produce 2 streams (over RTSP), and only the 2nd carries MJPEG:

• Stream 1: H.265 or H.264
• Stream 2: H.265, H.264 or MJPEG

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[Saxon Milton]

issue #159 will need to be addressed

[Saxon Milton]

Assigned to @Saxon Milton

[Saxon Milton]

Resolved in PR #289