HTTP response code for Redirect not readily discoverable

[pranavkm]

From dotnet/aspnetcore#1941

Pressing Ctrl+K, Ctrl+I (show intellisense) on a MVC Redirect() method doesn't display whether it uses HTTP 307 or 302. This important detail should be readily visible.

Likewise, pressing F12 on Redirect and then F12 on its return type RedirectResult shows the RedirectResult class definition with no documentation whatsoever. At a minimum the HTTP response code (based on whether a permanent redirect) should be shown in the XML documentation.

[Eilon]

Yeah let's put the HTTP status codes in the doc comments for our various helper methods on ControllerBase.cs.

[Eilon]

Done?