reduce panelization to 2 panels
As discussed, we only need two panels, one for the image and one for the transcription (that can be wysiwyg (Robin's) or straight (Hassan's). Since the layout segmentation interface can zoom we do not need the clean page interface anymore. Neither do we need a separate panel for bw. However, we do need buttons that allow the user to overlay (or not) combinations of: a) the type of image (color, grayscale, bw) b) the baselines c) the boundary polygons masks d) the regions e) the reading order indications