R1:b116861b1698

Add draft support to ApplicationTransactions

Summary:
When previewing, save drafts. When loading objects, restore drafts if they are available.

Depends on: D665

Test Plan:
- Viewed a Mock.
- Typed text into the comment box.
- Reloaded the page.
- Text still there.
- Hit submit, got my comment.
- Reloaded the page.
- Draft correctly deleted.
- Repeated for Macros.

Reviewers: btrahan, chad, vrana

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2104

Differential Revision: https…