Make PhabricatorRepositoryCommmit schema changes for audit

Summary:
  - Add a proper mailKey field to make these things mailable. Backfill all
existing objects.
  - Denormalize authorPHID to the commit object so we can query by it
efficiently in a future diff. We currently use the search engine to drive
"commits by author" but that's not so good for audit, which needs more
constraints.
  - Add an overall audit status field so we can efficiently query "commits that
needs your attention".
  - Add enough code to convince myself that these fields are basically
reasonable and work correctly.

Test Plan:
  - Ran schema upgrades. Checked database state afterward.
  - Ran "reparse.php --owners --herald" to verify worker changes.
  - Looked at a commit, altered aggregate status via audits / reparse.php,
verified it responded correctly.

Reviewers: btrahan, jungejason

Reviewed By: jungejason

CC: aran, epriestley, nh

Maniphest Tasks: T904

Differential Revision: https://secure.phabricator.com/D1706

resources/sql/patches/110.commitaudit.sql

@@ -0,0 +1,11 @@
+ALTER TABLE phabricator_repository.repository_commit
+  ADD mailKey VARCHAR(20) NOT NULL;
+
+ALTER TABLE phabricator_repository.repository_commit
+  ADD authorPHID VARCHAR(64) BINARY;
+
+ALTER TABLE phabricator_repository.repository_commit
+  ADD auditStatus INT UNSIGNED NOT NULL;
+
+ALTER TABLE phabricator_repository.repository_commit
+  ADD KEY (authorPHID, auditStatus, epoch);