Replace ColorRamp with HSLColor everywhere.

Fixes:
* Nuclear-purple color exploit.
* #3247.
* Removes a bunch of unnecessary color conversions every frame.

Caveats:
* The ramp range is now defined on the palette, so ramps can no longer be set per-player (may impact maps which define custom colors).
* It's no longer possible to perfectly recreate the original WW color ramps (I doubt we care).
* The old ColorRamp setting isn't migrated, so players will lose their color settings.

OpenRA.FileFormats/FieldLoader.cs

@@ -148,15 +148,15 @@ namespace OpenRA.FileFormats
 				return InvalidValueAction(x,fieldType, field);
 			}
 
-			else if (fieldType == typeof(ColorRamp))
+			else if (fieldType == typeof(HSLColor))
 			{
 				var parts = x.Split(',');
-				if (parts.Length == 4)
-					return new ColorRamp(
+				// Allow old ColorRamp format to be parsed as HSLColor
+				if (parts.Length == 3 || parts.Length == 4)
+					return new HSLColor(
 						(byte)int.Parse(parts[0]).Clamp(0, 255),
 						(byte)int.Parse(parts[1]).Clamp(0, 255),
-						(byte)int.Parse(parts[2]).Clamp(0, 255),
-						(byte)int.Parse(parts[3]).Clamp(0, 255));
+						(byte)int.Parse(parts[2]).Clamp(0, 255));
 
 				return InvalidValueAction(x, fieldType, field);
 			}