Convert "Account" and "Date and Time" settings to EditEngine

Summary:
Ref T4103. This pretty much replaces these panels in-place with similar looking ones that go through EditEngine.

This has a few rough edges but they're pretty minor and/or hard to hit (for example, when editing another user's settings, the crumbs have a redundant link in them).

Test Plan:

• Edited my own settings.
• Edited a bot user's settings.
• Tried to edit another user's settings (failed).

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T4103

Differential Revision: https://secure.phabricator.com/D16017