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/Blowfish.cs

@@ -47,7 +47,7 @@ namespace OpenRA.FileFormats
 
 		delegate void CipherFunc( ref uint a, ref uint b );
 
-		uint[] RunCipher(uint[] data, CipherFunc f)
+		static uint[] RunCipher(uint[] data, CipherFunc f)
 		{
 			uint[] result = new uint[data.Length];
 
@@ -120,7 +120,7 @@ namespace OpenRA.FileFormats
 			a ^= bf_f(b) ^ m_p[n];
 		}
 
-		uint SwapBytes(uint i)
+		static uint SwapBytes(uint i)
 		{
 			i = (i << 16) | (i >> 16);
 			i = ((i << 8) & 0xff00ff00) | ((i >> 8) & 0x00ff00ff);