Make profile menu /edit/ requests explicitly 404

Summary:
See D17160. Previously, the /edit/ route was never linked, but fataled when accessed. Make it 404 instead.

Also, fix an issue where editing "Application" menu items would fail because they didn't have a viewer.

Test Plan:

• Hit /edit/, got a 404.
• Edited an "Application" item.
• Moved, added, deleted, and edited other items.

Reviewers: chad

Reviewed By: chad

Differential Revision: https://secure.phabricator.com/D17165