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/tracks/_form.html.haml

@@ -0,0 +1,15 @@
+.row
+  .col-md-12
+    .page-header
+      %h1
+        -if @track.new_record?
+          New
+        = @track.name
+        Track
+.row
+  .col-md-12
+    = semantic_form_for(@track, :url => (@track.new_record? ? admin_conference_tracks_path : admin_conference_track_path(@conference.short_title, @track))) do |f|
+      = f.input :name
+      = f.input :color, :input_html => {:size => 6, :type => "color"}, :required=> true
+      = f.input :description, :input_html => {:rows => 2, data: { provide: "markdown-editable" } }, hint: markdown_hint
+      = f.action :submit, as: :button, button_html: { class: 'btn btn-primary' }