OO-3523: disable the possibility to skip the launch page in LTI course element if the configuration at the LMS level say so

OO-3532, OO-3532: add a third queue especially for deletion and export of users to not disturb the other services, export participant folder's drop box of users

OO-3477: remove uncalculated statistics, remove user property from logging table in setup script, adapt creation and update of the temporary table for course statistics

OO-3489, OO-3490, OO-3491, OO-3495, OO-3499, OO-3500, OO-3501: finish the export process, delete files after zipping, send email... and more exported data

OO-3489, OO-3492, OO-3493, OO-3494, OO-3496, OO-3497: infrastructure to export user data, export  portraits, notes, personal folder, calendars, subscriptions, delete calendars after usser deletion

OO-3477: really remove initial author from repository entry, update course log with the new policy of user properties, springify export manager and co., make logging object annotation based

OO-3473	: delete the temporary files only at the end of the wizard and not after the first created element

OO-3472: rewrite the delete routine to delete only the file of the edited checkbox, implement a check to not delete the file if it's used by an other checkbox

OO-3469: better check variable in velocity template, check if the candidate session exists in disposing phase

OO-3457: only use the latest candidate session in the correction workflow and don't use a cached one

OO-3425: in the publish process, delete the offer and not the offer access as in the access configuration panel