Rework decoration renderable traits:

- Removed implicit pip definitions and IPips interface.
  New decoration traits have been added to render them.
  Pip types are no longer hardcoded in OpenRA.Game.

- Decoration rendering is now managed by SelectionDecorations(Base),
  which allows us to remove assumptions about the selection box
  geometry from the decoration traits.

- RenderNameTag has been replaced by WithNameTagDecoration, which is
  an otherwise normal decoration trait.

- Unify the configuration and reduce duplication between traits.

- Removed hardcoded references to specific selection box renderables.

- Remove legacy cruft.

OpenRA.Mods.Common/Traits/World/ResourceType.cs

@@ -63,9 +63,6 @@ namespace OpenRA.Mods.Common.Traits
 		[Desc("Allow resource to spawn on ramp tiles.")]
 		public readonly bool AllowOnRamps = false;
 
-		[Desc("Harvester content pip color.")]
-		public PipType PipColor = PipType.Yellow;
-
 		void IMapPreviewSignatureInfo.PopulateMapPreviewSignatureCells(Map map, ActorInfo ai, ActorReference s, List<Pair<MPos, Color>> destinationBuffer)
 		{
 			var tileSet = map.Rules.TileSet;