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- RenderNameTag has been replaced by WithNameTagDecoration, which is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/Widgets/WorldInteractionControllerWidget.cs

@@ -64,7 +64,8 @@ namespace OpenRA.Mods.Common.Widgets
 			if (selectionDecorations == null)
 				return;
 
-			selectionDecorations.DrawRollover(unit, worldRenderer);
+			foreach (var r in selectionDecorations.RenderRolloverAnnotations(unit, worldRenderer))
+				r.PrepareRender(worldRenderer).Render(worldRenderer);
 		}
 
 		public override void Draw()