kit_model cleanup
removed redundant test
add method to pubsub to remove all callback linked to a specific event
prevents the addition to the tube of a tube with the wrong role.
transformed the DOM events into PubSub events (and therefore more easily testable).
generalised the use of 'alert.js' to display the user messages.
Merge pull request #224 from benoitmangili/selection_page_can_only_tube_of_one_given_role

Selection page can only tube of one given role