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.Game/Server/Server.cs

@@ -337,9 +337,9 @@ namespace OpenRA.Server
 			if (pr == null)
 				return;
 			if (pr.LockColor)
-				c.ColorRamp = pr.ColorRamp;
+				c.Color = pr.Color;
 			else
-				c.ColorRamp = c.PreferredColorRamp;
+				c.Color = c.PreferredColor;
 			if (pr.LockRace)
 				c.Country = pr.Race;
 			if (pr.LockSpawn)