Touch up Subscriber List Dialog

Summary: Reduces images in ObjectLists to 40px over 50px, adds ability to show stackable lists in dialogs. Fixes T4891

Test Plan:
Tested People, Projects, Subscriber lists.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: epriestley, Korvin

Maniphest Tasks: T4891

Differential Revision: https://secure.phabricator.com/D9426