Rendering Algorithms

Added rapid motion rendering algorithm, now renamed to the rasterizer, that performs efficient motion blurring by shading geometry at a single point in time, and caching and re-using the results at multiple points that the object moves across. It is enabled with the scanline rapid statement in the options, or the -scanline rapid command-line option. A new samples collect option statement controls second-stage sample compositing.
Implemented scene data swapping to disk, effectively extending available memory by a region on disk. It is enabled and set up with the -swap_dir and -swap_limit command-line arguments.
The state variable is now interpolated from explicit motion vectors (but not motion transformations) if motion blurring is turned off.
Shadowmap files now contain extra information at the end of the regular depth data that defines a coordinate system for reloading the shadow map into a different scene.