Add CSV download for ordergroups

app/views/admin/ordergroups/index.html.haml

@@ -2,6 +2,9 @@
 
 - content_for :actionbar do
   = link_to t('.new_ordergroup'), new_admin_ordergroup_path, class: 'btn btn-primary'
+  = link_to url_for(search: params[:q], format: :csv), class: 'btn' do
+    = glyph :download
+    CSV
 
 - content_for :sidebar do
   %p= t('.first_paragraph', url: link_to(t('.new_ordergroups'), new_admin_ordergroup_path)).html_safe
@@ -12,4 +15,4 @@
     = text_field_tag :query, params[:query], class: 'input-medium search-query',
       placeholder: t('admin.search_placeholder')
 #ordergroups
-  = render "ordergroups"
+  = render "ordergroups"