Subscriptions - make a dialog for massive subscription lists

Summary: Ref T4430. This just deploys it on the property lists. (Help on how to do translations better? I tried a more traditional pht('%s, %s, %s, and %d other(s)') but I think the string lookup assumes the %d comes as the second param or something?)

Test Plan: Made a Maniphest Task with a hojillion subscribers and noted the working dialogue. Also made a Pholio Mock with lots of subscribers and it worked.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: aran, epriestley, Korvin, chad

Maniphest Tasks: T4430

Differential Revision: https://secure.phabricator.com/D8525