Issue 4099 add a preference for the preferred locale for a user.

This adds the preferred locale user preference, currently the ability to edit this preference is controlled by roll out.

https://code.google.com/p/otwarchive/issues/detail?id=4099
The HTML and indenting gets a little wonky here. Start on line 80, it should be:
```
    </li>
  </ul>
</fieldset>
<fieldset>
  <dl>
    <dt><%= f.label :skin_id, ts('Your site skin') %> <%= link_to_help 'skins-basics' %>:</dt>
    <dd>
      <span class="actions"><%= link_to ts('Public Site Skins'), skins_path %></span>
      <%= f.select :skin_id, @available_skins.collect{|s| [s.title, s.id]} %>
    </dd>

    <dt><%= f.label :time_zone, ts('Your time zone: ') %></dt>
    <dd><%= f.time_zone_select :time_zone, nil, :default => Time.zone.name %></dd>

    <dt><%= f.label :work_title_format, ts('Browser page title format') %> <%= link_to_help 'work_title_format' %>:</dt>
    <dd><%= f.text_field :work_title_format %></dd>
  </dl>
</fieldset>
```