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.Game/FileFormats/VqaReader.cs

@@ -257,7 +257,7 @@ namespace OpenRA.FileFormats
 
 		int cachedFrame = -1;
 
-		void DecodeFrameData( int frame )
+		void DecodeFrameData()
 		{
 			cachedFrame = currentFrame;
 			for (var y = 0; y < blocks.Y; y++)
@@ -280,7 +280,7 @@ namespace OpenRA.FileFormats
 			get
 			{
 				if (cachedFrame != currentFrame)
-					DecodeFrameData(currentFrame);
+					DecodeFrameData();
 
 				return frameData;
 			}