scene model and associated business to store scene data in an arbitrary
set of blocks rather than fixed arrays; finally stuck a fork in scene
width and height as well as view width and height along with origin offset
and a few other now obsolete bits.
git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@2434 542714f4-19e9-0310-aa3c-eee0fc999fb1
Michael Bayne