General uncontroversial cleanup:

- Made private methods static where possible (runtime can elide checking the object for null).
- Declared attribute classes as sealed (allows reflection on attributes to complete faster).
- Moved some static cctor's into field initializers (static cctor's are slower than static field initializers).
- Made classes static if they contained only static methods (can't create instances of useless objects).
- Use inferable Exts.Lazy and not new Lazy<T>().
- Added required STAThread attribute to CrashDialog.
- Removed unused parameters in private methods.
- Added Serializable attribute to exceptions.
- Added parameter name in calls to ArgumentNullException.
- Use of as operator instead of is + cast.
- Changed (x as Foo).Bar anti-pattern into ((Foo)x).Bar. Results in sensible cast exceptions on error rather than null dereferences.
- Removed unused method in NullShader.

OpenRA.Mods.RA/Scripting/Global/TriggerGlobal.cs

@@ -22,7 +22,7 @@ namespace OpenRA.Mods.RA.Scripting
 	{
 		public TriggerGlobal(ScriptContext context) : base(context) { }
 
-		ScriptTriggers GetScriptTriggers(Actor a)
+		static ScriptTriggers GetScriptTriggers(Actor a)
 		{
 			var events = a.TraitOrDefault<ScriptTriggers>();
 			if (events == null)

OpenRA.Mods.RA/Scripting/LuaScriptInterface.cs

@@ -102,7 +102,7 @@ namespace OpenRA.Mods.RA.Scripting
 			return Activator.CreateInstance(type, argsArray);
 		}
 
-		object[] ConvertArgs(LuaTable args)
+		static object[] ConvertArgs(LuaTable args)
 		{
 			var argsArray = new object[args.Keys.Count];
 			for (var i = 1; i <= args.Keys.Count; i++)

OpenRA.Mods.RA/Scripting/Media.cs

@@ -14,7 +14,7 @@ using OpenRA.Widgets;
 
 namespace OpenRA.Scripting
 {
-	public class Media
+	public static class Media
 	{
 		public static void PlayFMVFullscreen(World w, string movie, Action onComplete)
 		{