Remove Scale from IRenderable interface.

It is no longer used, and isn’t implemented for most renderables.

OpenRA.Game/Graphics/SelectionBarsRenderable.cs

@@ -30,12 +30,10 @@ namespace OpenRA.Graphics
 
 		public WPos Pos { get { return pos; } }
 
-		public float Scale { get { return 1f; } }
 		public PaletteReference Palette { get { return null; } }
 		public int ZOffset { get { return 0; } }
 		public bool IsDecoration { get { return true; } }
 
-		public IRenderable WithScale(float newScale) { return this; }
 		public IRenderable WithPalette(PaletteReference newPalette) { return this; }
 		public IRenderable WithZOffset(int newOffset) { return this; }
 		public IRenderable OffsetBy(WVec vec) { return new SelectionBarsRenderable(pos + vec, actor); }