Fluid ctors

This is an example of what I was talking of by email If you look at the test you'll see how the fluid ctors let you build pretty complex messages in a single statement, without temporary variables and so on. It is much more useful when you mix it with LINQ queries, I have provide one examples in the tests). If you like this I can just go on and provide patches for all classes. Else I'll just keep these changes in my branch.