Simplify PaletteReference interface.

OpenRA.Mods.RA/Orders/PlaceBuildingOrderGenerator.cs

@@ -99,7 +99,7 @@ namespace OpenRA.Mods.RA.Orders
 
 				foreach (var r in preview)
 					r.Sprite.DrawAt(topLeft.ToPPos().ToFloat2() + r.Pos,
-									r.Palette.RowIndex(wr),
+									r.Palette.Index,
 									r.Scale*r.Sprite.size);
 
 				var res = world.WorldActor.Trait<ResourceLayer>();

OpenRA.Mods.RA/SupportPowers/ChronoshiftPower.cs

@@ -245,7 +245,7 @@ namespace OpenRA.Mods.RA
 						var targetCell = unit.Location + (xy - sourceLocation);
 						foreach (var r in unit.Render(wr))
                             r.Sprite.DrawAt(r.Pos - Traits.Util.CenterOfCell(unit.Location).ToFloat2() + Traits.Util.CenterOfCell(targetCell).ToFloat2(),
-								r.Palette.RowIndex(wr),
+								r.Palette.Index,
 								r.Scale*r.Sprite.size);
 					}
 				}