[FIX] google_calendar: Refresh code

- Google sync was dropped with new design
- Use new API alert/confirm dialogs
- The user was able to click on the button... by clicking next to it
    (remove the button template, create it in JS)
- Fix some exceptions in routes
- Convert CSS to LESS
- Update google tutorial

(google_calendar module needs some improvments, especially to give
meaningful error messages to the user when the google server sends
back errors)