Modernize blog UI

Summary:
Cleans up some of the mess I made in D3694. Basically:

  - All blogs have an "internal" view with posts that uses mobile-friendly UIs, etc., so we don't have to do as much work with skins -- they just have to look pretty.
  - Blogs now have a separate "live" view that we use to handle domains / skins.
  - Simplified some views and use IDs in some URLs for consistency.
  - Delete a bunch of edge/blogger/multi-blog code that's now obsolete.

Test Plan: Will attach screenshots.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T1373

Differential Revision: https://secure.phabricator.com/D3695

scripts/celerity/generate_sprites.php

@@ -218,6 +218,9 @@ $action_map = array(
   'subscribe-auto'    => 'icon/unsubscribe.png',
   'subscribe-add'     => 'icon/subscribe.png',
   'subscribe-delete'  => 'icon/unsubscribe.png',
+  'new'               => 'icon/page_white_put.png',
+  'world'             => 'icon/world.png',
+  'delete'            => 'icon/delete.png',
 );
 
 foreach ($action_map as $icon => $source) {