Slightly improve Buildable list in Harbormaster
Summary:
Ref T10457. This makes diffs/revisions show the revision as the buildable title, and commits show the commit as the title.
Previously, the title was "Buildable X".
Also makes icons/colors/labels more consitent.
Test Plan: {F1131885}
Reviewers: chad
Reviewed By: chad
Maniphest Tasks: T10457
Differential Revision: https://secure.phabricator.com/D15355