Update "Files" attachment table to show more attachment details and support detachment

Summary: Ref T13682. Make the "Attached" list in Files a bit more detailed, and add a "Detach" button.

Test Plan: Tried to detach unrelated, referenced, and attached files. Saw attached files detach.

Maniphest Tasks: T13682

Differential Revision: https://secure.phabricator.com/D21840