Update every 5 seconds

This makes the status symbols update every 5 seconds without needing to refresh the page.

It also turns the multiple HTTP requests into a single JSON one, increasing speed.
@kblanks You should use `.get('auto_update_interval', -1)` instead of just `['auto_update_interval']` so that users may disable this feature by simply removing the key from their config.

This also means that people who are updating from an older version don't get their stuff broken.