and the single participant folders

participant folder

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-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-3283: consolidate packages of RSS feed util and servlet for notifications, add and fix some missing i18n keys for notifications