Anonymous editing killswitch.

Syncs with config/ios.json at most once a day. Adjusts saving
interface to hide anon saving option if ios.json has flag for
disabling anon editing.

The sync code is done in generic fashion to make future sync
between server and bundled app json files painless.

Change-Id: Ia64c060806c14cbf08cacb3168af8f471c8de048