[tei-council] Simple : facsimile

The schema currently makes available within <facsimile> : surface, surfaceGrp, and zone, but not line. Is that balance about right? Should I restore <line> (which is sugar for <zone type="line">) ? Should I remove <surfaceGrp>? The purpose is to support a Simple document which contains just images and the lightest of transcriptions, such as you might get from a crowd sourcing transcription experiment for example, not to do full blown genetic transcriptions, obvs.