Clamp, scroll, scrollspeed, sliders

Reduced clamp duplication
Fixed scrolling speed issue
Modified scrollspeed slider to use a range
Fixed scrollspeed, volume, and sound sliders not showing current setting.

OpenRA.Game/Server/Exts.cs

@@ -33,15 +33,5 @@ namespace OpenRA.Server
 		{
 			return ts.Except( new[] { t } );
 		}
-
-		public static T Clamp<T>(this T val, T min, T max) where T : IComparable<T>
-		{
-			if (val.CompareTo(min) < 0)
-				return min;
-			else if (val.CompareTo(max) > 0)
-				return max;
-			else
-				return val;
-		}
 	}
 }