Implement update and history controllers in Phragment
Summary: Depends on D7726. This adds a history controller (for viewing a list of patches associated with a fragment) and an update controller, for creating a new patch of a fragment.
Test Plan: Updated and viewed history of fragments.
Reviewers: epriestley, Blessed Reviewers
Reviewed By: epriestley
CC: Korvin, epriestley, aran
Maniphest Tasks: T4205
Differential Revision: https://secure.phabricator.com/D7727