BibSched: new continuable error status for tasks
- New --stop-on-error/--continue-on-error CLI parameter for bibtasks.
- Handles CERROR and ERROR. CERROR is a continuable error that does not stop the queue. ERROR is a fatal error that stops the queue.
- BibUpload will decide whether to issue an ERROR or a CERROR. (closes #856)
- Always send emergency notification to CFG_SITE_ADMIN_EMAIL.
Co-authored-by: Samuele Kaplun <samuele.kaplun@cern.ch>