Use AphrontDialog for New/Move Phame Posts
Summary: Moves New Post and Move Post to be separate Controllers with Dialogs. Ref T9897
Test Plan: Move a post to a new blog, see message and see post. Click New Post, get dialog, pick blog, edit new post.
Reviewed By: epriestley
Maniphest Tasks: T9897
Differential Revision: https://secure.phabricator.com/D14698