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

src/applications/phame/controller/post/PhamePostViewController.php

@@ -155,14 +155,8 @@ final class PhamePostViewController extends PhameController {
       $actions[] = 'edit';
     }
 
-    $blog = PhameBlog::getRequestBlog();
-    if ($blog) {
-      $skin = $blog->getSkinRenderer();
-      $skin->setBlog($blog);
-      $skin->setIsExternalDomain(true);
-    } else {
-      $skin = new PhabricatorBlogSkin();
-    }
+    $skin = new PhabricatorBlogSkin();
+
     $skin
       ->setUser($user)
       ->setRequestURI($request->getRequestURI())