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.Mods.RA/Activities/Sell.cs

@@ -32,10 +32,7 @@ namespace OpenRA.Mods.RA.Activities
 				ns.Sold(self);
 
 			if (refund > 0 && self.World.LocalPlayer != null && self.Owner.Stances[self.World.LocalPlayer] == Stance.Ally)
-				self.World.AddFrameEndTask(
-					w => w.Add(new CashTick(refund, 30, 2,
-						self.CenterLocation,
-						self.Owner.ColorRamp.GetColor(0))));
+				self.World.AddFrameEndTask(w => w.Add(new CashTick(refund, 30, 2, self.CenterLocation, self.Owner.Color.RGB)));
 
 			self.Destroy();
 			return this;