Fix world visibility checks when shroud is disabled.
Introduce IRenderable.IsDecoration and AsDecoration.

These are used to filter *Renderables that shouldn't
be copied for things like highlight or shadow.
Parse sequence ZOffsets as a WRange.
Fix parsing of negative WRange.
Remove BelowUnits from C&C bibbed structures.

It interacts badly with the rewritten Bib trait.
Remove BelowUnits from D2K.
Remove BelowUnits from RA bibbed structures and crates.
Remove BibLayer and use sequences / RenderSprites instead.
Replace IOrderGenerator.RenderBeforeWorld with world-sorted .Render.

Range circles have been moved to RenderAfterWorld for now.
Remove obsolete ITooltip.Stance.
Add IMove interface.

Fixes Rallypoints for aircraft.
Fix z-ordering of FrozenActorProxy.
Don't flash bibs when targeting buildings.
Merge pull request #3665 from pchote/frozen-fog-prereqs

Rework bibs (again).