Add a basic web UI for intracluster sync logs

Summary: Depends on D19798. Ref T13216. This puts at least a basic UI on top of sync logs.

Test Plan:
Viewed logs from the web UI and exported data. Note that these syncs are somewhat simulated since I my local cluster is somewhat-faked (i.e., not actually multiple machines).

{F5995899}

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13216

Differential Revision: https://secure.phabricator.com/D19799