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/Web/Views/Account/Lockout.cshtml

@@ -0,0 +1,8 @@
+@{
+    ViewData["Title"] = "Locked out";
+}
+
+<header>
+    <h2 class="text-danger">@ViewData["Title"]</h2>
+    <p class="text-danger">This account has been locked out, please try again later.</p>
+</header>