Fix test form and move to public directory to make it easily available

The form is helpful for development. moving it to the public folder makes
it available from http://localhost:3000/testform.html

app/views/forms/form.html.erb

@@ -1,7 +1,7 @@
 <h1><%= @form.title %></h1>
 
 <%= form_with url: submission_url(@form), action: 'post', authenticity_token: false, local: true, html: { enctype: 'multipart/form-data' } do %>
-  <% @form.header_values.each do |header| %>
+  <% @form.spreadsheet_headers.each do |header| %>
     <p>
       <label><%= header %>
       <%= text_field_tag header %>