Added possibility to search for 'NotTicketFlags', thanks to Moritz Lenz.
Only auto-set seen flag if article was created by an agent.
Fixed: Backup script should delete incomplete backups (bug#10665).

Conflicts:
	CHANGES.md
	scripts/backup.pl
Fixed some issues with NeedSpellCheck, thanks to S7.
Follow-up fix for bug#10813: add missing destructor.
Merge remote-tracking branch 'upstream/master' into otrs-master