Add a way to expose all image statues.

This is triggered by a key accel ctrl-s on the lighttable view.

This is a simple key accel to activate or not the image statuses overlay on the lighttable. That is by hitting ctrl-s the stars, rejected status and developed status are shown on all displayed image and not only when hovering.

If there is no objection I'll merge this over the week-end, this is really something I miss.