Add bin/harbormaster to make builds easier to debug

Summary:
Ref T1049. Adds bin/harbormaster and bin/harbormaster build for applying plans from the console. Since this gets --trace, it's much easier to debug what's going on.

This doesn't work properly with some of the Drydock steps yet, I need to look at those. I think setRunAllTasksInProcess probably obsoletes some of the mechanisms. It might also not work with "Wait for Builds" but I didn't check.

Test Plan: Used bin/harbormaster to run a bunch of builds. Ran builds from web UI.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T1049

Differential Revision: https://secure.phabricator.com/D7825