R1:aad6b57c36f8

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…