Adding 2FA Authenticator Support (#66)

* Adding support for 2fa, more auth options

* WIP getting auth stuff working

* Added Manage views. 2FA working now for MVC app.

* Switching to using a controller for no-UI logout scenario

* Adding Razor Pages impl of 2FA auth stuff. Works.

src/WebRazorPages/Pages/Account/LoginWithRecoveryCode.cshtml

@@ -0,0 +1,29 @@
+@page
+@model LoginWithRecoveryCodeModel
+@{
+    ViewData["Title"] = "Recovery code verification";
+}
+
+<h2>@ViewData["Title"]</h2>
+<hr />
+<p>
+    You have requested to log in with a recovery code. This login will not be remembered until you provide
+    an authenticator app code at log in or disable 2FA and log in again.
+</p>
+<div class="row">
+    <div class="col-md-4">
+        <form method="post">
+            <div asp-validation-summary="All" class="text-danger"></div>
+            <div class="form-group">
+                <label asp-for="Input.RecoveryCode"></label>
+                <input asp-for="Input.RecoveryCode" class="form-control" autocomplete="off" />
+                <span asp-validation-for="Input.RecoveryCode" class="text-danger"></span>
+            </div>
+            <button type="submit" class="btn btn-default">Log in</button>
+        </form>
+    </div>
+</div>
+ 
+ @section Scripts {
+    @await Html.PartialAsync("_ValidationScriptsPartial")
+}