Add a basic view for repository pull logs

Summary:
Depends on D18912. Ref T13046. Add a UI to browse the existing pull log table.

The actual log still has some significant flaws, but get the basics working.

Test Plan:

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13046

Differential Revision: https://secure.phabricator.com/D18914