Phragment v0
Summary: Ref T4205. This is an initial implementation of Phragment. You can create and browse fragments in the system (but you can't yet view a fragment's patches / history).
Test Plan: Clicked around and created fragments.
Reviewers: epriestley, #blessed_reviewers
Reviewed By: epriestley
CC: Korvin, epriestley, aran
Maniphest Tasks: T4205
Differential Revision: https://secure.phabricator.com/D7726