add basic user revert functionality

app/views/user_reverts/new.html.erb

@@ -0,0 +1,19 @@
+<div id="c-users">
+  <div id="a-new">
+    <h1>Revert Changes</h1>
+
+    <p>You are about to revert all changes made by <%= link_to_user @user %>. Continue?</p>
+
+    <%= form_tag(user_revert_path) do %>
+      <%= hidden_field_tag :user_id, params[:user_id] %>
+
+      <%= submit_tag "Yes" %>
+    <% end %>
+  </div>
+</div>
+
+<%= render "users/secondary_links" %>
+
+<% content_for(:page_title) do %>
+  User Revert - <%= Danbooru.config.app_name %>
+<% end %>