Implement consistent admin interface

* Consistent route/model/controller/view layout
* Get rid of unused photos, speakers, dietchoices, social_events controllers
* Drop unused :public from Rooms and :description from CallForPapers

app/views/admin/sponsorship_levels/_form.html.haml

@@ -1,2 +1,14 @@
-= f.input :title
-= f.action :submit, as: :button, button_html: { class: 'btn btn-primary' }
+.row
+  .col-md-12
+    .page-header
+      %h1
+        - if @sponsorship_level.new_record?
+          New
+        Sponsorship Level
+        = @sponsorship_level.title
+.row
+  .col-md-8
+    = semantic_form_for(@sponsorship_level, :url => (@sponsorship_level.new_record? ? admin_conference_sponsorship_levels_path : admin_conference_sponsorship_level_path(@conference.short_title, @sponsorship_level))) do |f|
+      = f.input :title
+      %p.text-right
+        = f.action :submit, as: :button, button_html: { class: 'btn btn-primary' }