title: Activeadmin: Setting the default prompt for all select fields
body: <p>I have a two select fields and their default options are blank so I would like to set all of them to 'Choose one'. I can do it for individual fields but I want to do it in the config somehow (avoiding the redundancy).</p>
  
  <pre><code>  form do |f|
      f.inputs "Item" do
        f.input :field_1, :prompt =&gt; 'Choose one', :foo
        f.input :field_2, :prompt =&gt; 'Choose one', :bar
      end
    end
  </code></pre>
  
  <p>How do I do this? :)</p>
  
  <p>Edit: These prompts would be used on many forms. It really needs to be a config thing.</p>