Make various minor Harbormaster UI improvements

Summary: Ref T1049. Tweaks some of the UI and code to improve / clean it up a bit.

Test Plan: Ran build plans, browsed UI.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T1049

Differential Revision: https://secure.phabricator.com/D8603