Remove bogus Require<>s.
Move RenderSprites and RenderSimple into Mods.RA.
ToLowerInvariant RenderSprites.GetImage.

Some mods (d2k) define bogus-case sequence names.
Reorganize IBodyOrientation.
Introduce actor previews for PBOG and the editor.
Account for building turret facing in actor previews.
Account for walls in actor previews.
Account for infantry in actor previews.
Add support for turrets in actor previews.
Add support for idle overlays in actor previews.
Add support for rotors in actor previews.
Add support for voxels in actor previews.
remove unneccessary build-top sequences
HACK: more visible pbog.