* Schema change: Removing courses_terms.attendees couter
* Replacing courses_terms.attedess by a subquery counting the people
depending on the booking_state_name.
* Moving columns on subscription page.
* Showing certificate buttons only if the user selected the course or is
already subscribed.
* Changing certificate status instantly with a email confimation is the
course is already subscribed.
* Logging users directly in after account activation.
* If no addresses are defined then the courses are hidden until an
address is saved.
* Changing some alert boxes content and style for users.
* Optimizing some queries by hand.
* Changing preliminary email confirmation to have additional information
(address, name, ...).