fix bugs in ion cannon

OpenRA.Mods.Cnc/Effects/IonCannon.cs

@@ -44,7 +44,7 @@ namespace OpenRA.Mods.Cnc.Effects
 		public IEnumerable<Renderable> Render()
 		{
 			yield return new Renderable(anim.Image,
-				Target - new float2(.5f * anim.Image.size.X, anim.Image.size.Y - Game.CellSize),
+				Util.CenterOfCell(Target) - new float2(.5f * anim.Image.size.X, anim.Image.size.Y - Game.CellSize),
 				"effect");
 		}
 	}

mods/cnc/system.yaml

@@ -23,6 +23,7 @@ Player:
 		BeginChargeSound: ionchrg1.aud
 		EndChargeSound: ionredy1.aud
 		LaunchSound: ion1.aud
+		SelectTargetSound: select1.aud
 	
 World:
 	ScreenShaker: