GFOA\Request

Added the GFOA\Request class, partly to solve a problem with the People controller, and partly to reduce coupling.

The issue with the People controller was that, if someone attempted to navigate to it, but was prompted to login, once they'd successfully logged in, after the Authenticator handled the login POST, the state of that request was still that of a POST.  Therefore the People controller attempted to edit/create a person, failed validation, and caused a 400 Bad Request.

The solution was to add/inject the GFOA\Request object, and have its IsPost method only return true once, returning false thereafter.  The class also has a HandlePost method, which suppresses the request from being identified as a POST without calling IsPost.