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-3436: if the admin user is not configured or doesn't exist, do nothing but write a message in log

OO-3016: optimize "Linked with course" in the business group search, reduce the number of relationships to course which are search every time

OO-2975: delete imported calendar after course, group and user deletion, implement a check every 10 runs to remove deprecated imported calendar, append the job to the scheduler

OO-2878: add attachment to the info messsages, add the possibility to send the emails only to owners, coaches or participants and not all of them

OO-2868 improve copy/paste links by wrapping them in an input field for proper selection without trailing whitespace