Added: the layout editor shows your background. The boxes are arranged over the
picture the clock will actually draw, at the fit it will use, so what is cropped
in the editor is what will be cropped on the clock. It is dimmed a little so the
thin outlines stay readable, and a tick under the canvas turns it off when a busy
picture gets in the way.

Added: the Fields list is the order the boxes lie in. Each field now has arrows to
move it up and down: the top of the list is in front, the bottom is underneath. If
two boxes overlap, this is what decides which one covers the other.
