Remove comment plugins from Phame
Summary: Cleaning up house, may revisit in a v2. Removes ability to set Disqus or Facebook comments as comment system on Phame Posts.
Test Plan: Create blog, create post, edit blog, view live pages.
Reviewers: epriestley
Reviewed By: epriestley
Subscribers: btrahan, Korvin
Maniphest Tasks: T9746
Differential Revision: https://secure.phabricator.com/D14448