Summary:
- Add a "delete" operation. Delete is just a special edit which removes the
page from indexes and shows a notice that the document has been deleted.
- When a user deletes all the content on a page, treat it as a delete.
- When a conduit call deletes all the content on a page, treat it as a delete.
- Add page status to Conduit.
- Add change type field to history.
- Added a couple of constants to support a future 'move' change, which would
move content from one document to another.
Test Plan:
- Verified deleted pages vanish from the document index (and restoring them
puts them back).
- Verified deleted pages show "This page has been deleted...".
- Created, edited and deleted a document via Conduit.
- Deleted pages via "delete" button.
- Deleted pages via editing content to nothing.
Reviewers: btrahan, jungejason
Reviewed By: btrahan
CC: skrul, aran, btrahan, epriestley
Maniphest Tasks: T680
Differential Revision: 1230
