Summary: Fixes T3189. Now if you say #projects in a commit message they will associate nicely with the commit. Also we record transactions about all this project editing fun.
Test Plan: tested migration by associating some projects with commits and verifying they still showed up post migration. tested adding / removing projects by doing so from the UI, noting transactions written nicely as well
Reviewers: epriestley
Reviewed By: epriestley
Subscribers: Korvin, epriestley
Projects: #projects
Maniphest Tasks: T3189
Differential Revision: https://secure.phabricator.com/D10877
