C#: Renames to follow .NET naming conventions

Renamed C# types and members to use PascalCase and follow .NET naming conventions.

doc/classes/Image.xml

@@ -525,7 +525,7 @@
 				var img = new Image();
 				img.Create(imgWidth, imgHeight, false, Image.Format.Rgba8);
 
-				img.SetPixelv(new Vector2i(1, 2), Colors.Red); // Sets the color at (1, 2) to red.
+				img.SetPixelv(new Vector2I(1, 2), Colors.Red); // Sets the color at (1, 2) to red.
 				[/csharp]
 				[/codeblocks]
 				This is the same as [method set_pixel], but with a [Vector2i] argument instead of two integer arguments.