Rewrite TS minimap rendering:

* Rename LeftColor and RightColor to MinColor and MaxColor
  These are mapped from LowRadarColor and HighRadarColor in
  the original inis, and appear to be used to set the bounding
  values for selecting a random colour, NOT for left/right
  pixels (which caused noticeably wrong banding).

* Adjust brightness based on terrain height.
  MinHeightColorBrightness and MaxHeightColorBrightness
  were chosen by trial/error to match the original
  map preview rendering.

OpenRA.Mods.Common/UpdateRules/UpdatePath.cs

@@ -65,6 +65,7 @@ namespace OpenRA.Mods.Common.UpdateRules
 				new SpawnActorPowerDefaultEffect(),
 				new RemoveConditionManager(),
 				new ConvertSupportPowerRangesToFootprint(),
+				new UpdateTilesetColors(),
 			})
 		};