More HashSet trait fields & Lint support

OpenRA.Mods.Common/Traits/ExternalCaptures.cs

@@ -20,7 +20,7 @@ namespace OpenRA.Mods.Common.Traits
 	class ExternalCapturesInfo : ITraitInfo
 	{
 		[Desc("Types of actors that it can capture, as long as the type also exists in the ExternalCapturable Type: trait.")]
-		public readonly string[] CaptureTypes = { "building" };
+		public readonly HashSet<string> CaptureTypes = new HashSet<string> { "building" };
 
 		[Desc("Destroy the unit after capturing.")]
 		public readonly bool ConsumeActor = false;