Fix #4571: Show banner when email verification is required.

* Show a banner if the user is restricted because they signed up from a
  proxy or VPN.

* Add an option to resend the confirmation email if your account has an
  unverified email address.

app/views/emails/verify.html.erb

@@ -0,0 +1,20 @@
+<% page_title "Verify account" %>
+
+<div id="c-emails">
+  <div id="a-verify" class="fixed-width-container">
+    <h1>Verify account</h1>
+
+    <% if @user.is_restricted? %>
+      <p>Your account is restricted because you signed up from a VPN or proxy.
+      You can still use the site, but you won't be able to leave comments, edit
+      tags, or upload posts until you verify your account.</p>
+    <% end %>
+
+    <p>Click below to send an email to <strong><%= @email_address.address %></strong>
+    to verify your account.</p>
+
+    <%= edit_form_for(@user, method: :post, url: send_confirmation_user_email_path(@user)) do |f| %>
+      <%= f.submit "Send confirmation email" %>
+    <% end %>
+  </div>
+</div>