Modify rules to properly handle C# extension methods

[patrickfrancis]

C# supports extension methods, which are written separately from a class but act as if they're member methods. The syntax for an extension method is to include the target class as the first parameter, along with the "this" keyword. For example:

public static bool ContainsCallTo(this XContainer container, string functionName)

In this case, container should not be a Secondary Argument. It should perhaps be the Declared Class?