Converting cron job to use model for scheduler and slot
Improve event deletion when deleting a scheduler
CONTRIB-5182 Language of e-mail notifications

Do processing of multilang strings in the recipient's language
Cleaning up the backup/restore process
Fix timezone handling in remidner e-mails
Removing unused icons
Help string for guard time
Show additional fields in student view
Expand release notes
Bumping version number on master branch after 2.7 release
Adding more unit tests
Teacher view: Fixing the list of students available for scheduling