R1:0fd77783a49e

Add previews to ApplicationTransaction

Summary:
Implements previews for Macros and Pholio.

(Design is nonfinal -- kind of split the difference between `diff_full_view.png`, laziness, and space concerns. Next couple diffs will add more stuff here.)

Test Plan: {F28055}

Reviewers: btrahan, chad

Reviewed By: btrahan

CC: aran, vrana

Maniphest Tasks: T2104

Differential Revision: https://secure.phabricator.com/D4246