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/Manage/_Layout.cshtml

@@ -0,0 +1,23 @@
+@{ 
+    Layout = "/Views/Shared/_Layout.cshtml";
+}
+
+<h2>Manage your account</h2>
+
+<div>
+    <h4>Change your account settings</h4>
+    <hr />
+    <div class="row">
+        <div class="col-md-3">
+            @await Html.PartialAsync("_ManageNav")
+        </div>
+        <div class="col-md-9">
+            @RenderBody()
+        </div>
+    </div>
+</div>
+
+@section Scripts {
+    @RenderSection("Scripts", required: false)
+}
+