Add CellRegion and CellLayer classes to simplify map overlays.
Integrate CellRegion with Map, Viewport.
Use CellLayers for pathfinder debug.
Use CellLayers for ResourceLayer.
Use CellLayers for shroud.
Use CellLayer for ActorMap.
Use CellLayer for DomainIndex.
Use CellLayer for BuildingInfluence.
Use CellLayer for BridgeLayer.
Use CellLayer for custom terrain.
Use CellLayer for resources.
Use CellLayer for terrain.
Remove CellBounds from BuildableTerrainLayer and SmudgeLayer
Remove unused Map.IsInMap(x,y) overload.
Use CellLayer for pathfinding.
Remove the now-unused ExploredBounds optimization.
Simplify shroud range checks.