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/AI/AttackOrFleeFuzzy.cs

@@ -169,7 +169,7 @@ namespace OpenRA.Mods.RA.AI
 			return !double.IsNaN(attackChance) && attackChance < 30.0;
 		}
 
-		protected float NormalizedHealth(IEnumerable<Actor> actors, float normalizeByValue)
+		protected static float NormalizedHealth(IEnumerable<Actor> actors, float normalizeByValue)
 		{
 			var sumOfMaxHp = 0;
 			var sumOfHp = 0;
@@ -206,7 +206,7 @@ namespace OpenRA.Mods.RA.AI
 			return RelativeValue(own, enemy, 100, Average<Mobile>, (Actor a) => a.Trait<Mobile>().Info.Speed);
 		}
 
-		protected float RelativeValue(IEnumerable<Actor> own, IEnumerable<Actor> enemy, float normalizeByValue, 
+		protected static float RelativeValue(IEnumerable<Actor> own, IEnumerable<Actor> enemy, float normalizeByValue, 
 					Func<IEnumerable<Actor>, Func<Actor, int>, float> relativeFunc, Func<Actor, int> getValue)
 		{
 			if (!enemy.Any())