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

db/migrate/20141120205757_remove_public_from_room.rb

@@ -0,0 +1,5 @@
+class RemovePublicFromRoom < ActiveRecord::Migration
+  def change
+    remove_column :rooms, :public, :boolean, default: false
+  end
+end

db/migrate/20141121102656_remove_description_from_call_for_paper.rb

@@ -0,0 +1,5 @@
+class RemoveDescriptionFromCallForPaper < ActiveRecord::Migration
+  def change
+    remove_column :call_for_papers, :description, :text
+  end
+end