Fix dead column link and provide more milestone UI context

Summary:
Fixes T10287. Ref T10286.

• Link stuff properly.
• Generally, show "Parent (Milestone)" instead of "Milestone".
• This probably doesn't get 100% of getName() -> getDisplayName() swaps, but we can get those as we catch them.

Test Plan: See T10286. Also clicked stuff.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10286, T10287

Differential Revision: https://secure.phabricator.com/D15189