Search builds based on who kicked them off

Summary:
It's only natural for users to be interested their own builds. We are also building in support for other sources of builds, the only formally supported way to run a build right now is via Herald.

In our third party codebase, we designate an application as the "thing" that started builds which are scheduled and managed automatically by phabricator. I believe this is a common practice elsewhere in the codebase when you're at a loss for a real human identity and you need to apply some transactions.

Test Plan: Ran some builds manually and saw them show up under the list of things I've run. Looking up builds based on those that had been started by a herald rule.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D16353