OO-1733: clean up all possible references, the check to prevent deletion must happen before reaching the delete method of the service

OO-1645,OO-1595: refactor the personal configuration of calendars, the datamodel of imported calendars, make the description visible and editable...

OO-1647: remove auto-subscribe of course calendar, list of course which the user is member of and which have a calendar ( as configuration or as course element)

OO-1239: allow to delete all references of a resource in the delete process, check if the reference are orphans, managed, owned...

OO-1408: improve performance with native SQL queries, add all queries needed for authors to see their courses and the groups linked to their courses

OO-1182: pass the toolbar as constructor to initialize all sub controller with it, independent of the timing of this initialization

OO-990: only retrieve the roles once, use them for all access security control, retrieve the groups only if the roles coach, participant or waiting are there... to minimize the number of queries

OO-1000: fix an issue with the edition of coach role of course, fix some issues with the views of the coaching tool

OO-990: mostly fix of the authoring GUI, and unit tests, integrate the demo course to the test resource

OO-990: rework importation of course node with references, implement autowiring capabilities in controllers

OO-985: implements the view to retrieve the course and associated data of a user, filter and order by, clean up the code

OO-936: implements course element "check list", enhance the flexi-table with sort, filter and export, enhance publish process with an update step, upgrade pdfbox to version 1.84

OO-911, OO-912: implements the course node triggered buttons in assessment tool, implement bulk upload for tasks with selection of a group if needed