Document job_timeouts.create_process_failures

https://redmine.teklia.com/issues/7593

A new job_timeouts.create_process_failures setting in the YAML configuration is introduced in Arkindex 1.6.2, defaulting to 3600 seconds.

It must be documented in the YAML config reference, and a section should be added to the 1.6.2 upgrade notes to mention this new task, the new timeout setting, and the fact that it sends e-mails. The setting might be something that sysadmins need to tweak with, and e-mails are finicky too!