Move user editing/management actions to a separate "Manage" item, like projects

Summary: This improves consistency (by making this UI more similar to the projects UI) and gives us more flexibility the next time we update user profiles.

Test Plan:

Took all the actions (probably?) to check that all the redirects were updated.

Reviewers: chad

Reviewed By: chad

Differential Revision: https://secure.phabricator.com/D15104