Allow non-"formatted" friendly message for WebException (mtc900)

[mikeobrien]

There is a need to submit a raw friendly message that is not string.formattable. To do so, please add another constructor:

public WebException(HttpStatusCode status, string friendyMessage) :
base(friendyMessage)
{
Status = status;
}

Therefore, if there are no parameters, the string.format() method is never called and the friendly message can contain any combination of braces such as JavaScript code.