New artwork for the future ToD display

tod-schedule-* files each contains the individual ToD sky images for an entire schedule
tod-clouds-* files each contain cloud images that will be randomly overlaid on the sky image according to the expected lighting conditions of a given ToD
tod-template is a mask in the shape of the ToD window that will be used to crop any element it contains: ToD skies, clouds, terrain overlays, oversized unit sprites, …

Additional schedule images will be added later.