Add a basic pull event log for debugging repository cloning

Summary:
Ref T10228. This is currently quite limited:

  - No UI.
  - No SSH support.

My primary goal is to debug the issue in T10228. In the long run we can expand this to be a bit fancier.

Test Plan:
Made various valid and invalid clones, got sucess responses and not-so-successful responses, viewed the log table for general corresponding messages and broad sanity.

Ran GC via `bin/phd debug trigger`, no issues.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10228

Differential Revision: https://secure.phabricator.com/D15127

resources/sql/autopatches/20160128.repo.1.pull.sql

@@ -0,0 +1,14 @@
+CREATE TABLE {$NAMESPACE}_repository.repository_pullevent (
+  id INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
+  phid VARBINARY(64) NOT NULL,
+  repositoryPHID VARBINARY(64),
+  epoch INT UNSIGNED NOT NULL,
+  pullerPHID VARBINARY(64),
+  remoteAddress INT UNSIGNED,
+  remoteProtocol VARCHAR(32) COLLATE {$COLLATE_TEXT},
+  resultType VARCHAR(32) NOT NULL COLLATE {$COLLATE_TEXT},
+  resultCode INT UNSIGNED NOT NULL,
+  properties LONGTEXT NOT NULL COLLATE {$COLLATE_TEXT},
+  KEY `key_repository` (repositoryPHID),
+  KEY `key_epoch` (epoch)
+) ENGINE=InnoDB, COLLATE {$COLLATE_TEXT};