Support concrete bibs in D2K.
Add DamagedWithoutFoundation trait for building weathering.
Add BuildableTerrainLayer and LaysTerrain traits.
Add RemoveImmediately trait for things that should only exist for one tick.
Fix PBOG and Building to support concrete placement.
Don't notify when the world attacks your base.
Add buildable concrete and weathering to D2k. Fixes #2249.
Fix BuildingInfluence style nits.
Don't stomp over other building's influence.
Actors outside the world can't grant buildable area.