Reimplement user info page in React

Discard the AngularJS version. Support some more action types, e.g.
approve, close, delete.
Rename file.
Load and save user preferences.
Remember email-for-every-new-post preference.
Send notfs to people watching whole site.
Show 'Saving...', 'Saved'.
Merge branch 'topic-user-prefs-page'.
Upgrade to React 0.12.1, and -router and -bootstrap.